Økonomis
A set of Danish personal-finance calculators in a single static web page: compare investment account types, plan monthly investing and FIRE, track a portfolio, build a budget, and follow your net worth over time.
Live: https://simongsk.github.io/Finance-and-investment-tool/
All data stays in your browser's localStorage. There are no accounts, no server, and nothing is sent anywhere.
The tools
The menu has Oversigt at the top, then three groups: Værktøjer (Investering, Bolig & lån, Budget), Trackers (Formue, Månedsoverblik, Portefølje) and Hjælp (Indstillinger, Hjælp og spørgsmål, Giv feedback).
Oversigt
The start page. Each key-figure card opens the page its number comes from (Formue, Månedsoverblik, Portefølje, the FIRE calculator or Budget), and on larger screens shows a small line of what the number builds on over the last 12 months (CARD_SPARKS in overview-cards.js; hidden when it would touch the card's text, and never on phones), and tapping a bar in the net worth chart selects it and shows "Se [måned] →" under the chart — the link or a second tap on the same bar opens that month in Månedsoverblik, so a tap to see the value never jumps away. Shows net worth (with the change since the last status), the portfolio (this year's return), the monthly budget and how many months the emergency fund covers; net worth over time (all data by default, or the last 1, 3, 5, 10 … years — only periods your data covers are offered), goals, how assets are split, a short list of next steps (save this month's status, build a budget, take a backup …) that tidies itself — each step disappears when it's done and can be hidden with × (the month's status until next month, backup for 30 days, the emergency fund for 90 days, the getting-started steps for good), and the card is gone when nothing is left and shortcuts to every tool. Tilpas oversigt (the sliders icon next to the eye) chooses the four key figures at the top — each slot opens a list where its current card has a clear check and your other three cards are faintly marked with their slot, so choosing one swaps them —, grouped by where the number comes from: Formue (net worth, liquid wealth, pension, debt), Månedsoverblik (average growth per month, growth in % over the last year, growth this year), Portefølje (value, total invested, total return, dividends, return per year) and Budget (budget per month, emergency fund). On phones and tablets the chart comes first and the key figures under it.
Investering
ASK vs. Aktiedepot — Compares a lump sum in a Danish stock savings account (Aktiesparekonto, flat 17% yearly tax on gains, 174.200 kr. deposit limit) against the same sum in a regular depot (Aktiedepot, 27%/42% progressive tax on realised gains, no limit). The depot side uses the tax-optimal realisation strategy described below. Supports paying the ASK tax from outside the account, the doubled 27% threshold for married couples, and inflation-adjusted ("today's purchasing power") display.
Aktiedepot: fast + månedligt — A regular depot with an optional starting amount plus a fixed monthly contribution, again with the optimal realisation strategy. Shows total invested, net profit and percentage gain.
FIRE-beregner — How many years until a portfolio can sustain your yearly expenses under the 4% rule, given a starting amount, monthly contributions, expected return and inflation. The FIRE target grows with inflation, so the answer is in real terms. Hent mine tal fetches your numbers from Formue (cash and shares by default; pension and home equity can be ticked) and your yearly spending and monthly saving from the budget.
Pension — Projects a private pension pot to retirement after costs and the 15.3% PAL tax, then shows the monthly payout before and after tax, in today's money. Shows your folkepension age from your birth year (67–70 is legislated; higher ages are projections and labelled as such).
Porteføljetracker — Log your portfolio's value, cash, trades, deposits and dividends over time. Charts value vs. cumulative deposits, monthly buys/sells, and total return. Import and export as CSV. The Tilføj datapunkt panel can be folded away to its heading, and the choice is remembered.
Skattegrænse — Type in this year's numbers for your aktiedepot from your bank and see how close your aktieindkomst is to the 27 % limit (79.400 kr. in 2026, doubled for married couples), above which tax rises to 42 %. Aktieindkomst is realised gains minus losses, plus dividends and the year's gain on ETFs from the positive list (taxed on unrealised gains). Shows a progress bar, how much more gain you can realise at 27 %, and an estimated tax. The numbers are saved per tax year and included in the backup file. A simplified calculation; the annual tax statement is final.
Tips & viden — A beginner's guide in foldable sections: before you start, account types (aktiedepot, ASK, pension, børneopsparing), tax and the positive-list lookup (search Skattestyrelsens list by ISIN or name, loaded only when you search), shares vs funds vs ETFs vs bonds, sectors and their volatility, risk, a glossary (afkast, udbytte, GAK …) and company key figures from easy (market value, revenue) to technical (EBITDA, free cash flow, net debt/EBITDA). General knowledge, not advice.
Bolig & lån
Hvor meget kan jeg låne? — The highest home price you can buy given three limits: savings covering at least a 5% down payment plus purchase costs (2026 tinglysning fees included), your debt factor, and optionally a maximum monthly payment. Shows which limit binds and a full breakdown of loans and monthly payments after interest deduction.
Køb eller leje? — Year-by-year net worth when buying versus renting and investing the difference. Includes mortgage and bank loan, contribution fees, interest deduction, property tax, maintenance, price growth and selling costs.
Gældsafvikling — Enter your debts and an extra monthly payment to see when you're debt-free and how much interest you pay with the avalanche method (highest rate first), the snowball method (smallest balance first), or minimum payments only.
Budget
Build a monthly budget from itemised posts in 15 categories plus your own, each edited in its own dialog. Posts can be monthly, quarterly, half-yearly or yearly. Shows the split across needs / wants / savings against the 50/30/20 rule, and projects yearly savings. Udskriv overblik prints (or saves as PDF) a one-page overview of net worth, budget, loans, goals and portfolio; Download budget saves a CSV (opens in Excel or Numbers) with every post per month and per year plus a 50/30/20 summary, e.g. to show a financial advisor.
Månedsoverblik
Pick a year and a month (or the whole year) and see how each part of your net worth changed in that period: net worth, liquid wealth, pension, cash, shares, home equity, other and debt, each with start, end, change in kr. and %. A month is compared with the previous monthly status (the text says which dates, so a gap is visible); a whole year runs from the last status before 1 January. The portfolio's return for the same period comes from the portfolio tracker, with your own deposits taken out. Each category has a small trend line over the last year, and the year's best and worst month are shown under the key figures (a month after a skipped status counts as one step, e.g. "aug.–sep. (2 mdr.)"). Choosing Hele året shows Dit år i tal: the year's growth, best and worst month, months with growth, the portfolio's return, deposits and dividends, and Del som billede, which draws the year as a 1080 × 1350 image to share or save, with or without amounts.
On a phone you can swipe left or right to go to the next or previous month (or year, with Hele året), skipping months without a status; on a computer ←/→ do the same (adjacentPeriod in calc.js).
Dit år i farver shows the selected year as twelve squares, one per month: green when net worth rose and red when it fell, in four shades by size compared with the year's biggest change (yearColors in calc.js). A month without a status is dashed and the coming months are faint; pointing at or choosing a square shows the change (with "(2 mdr.)" when a status is missing before it), and clicking opens that month.
Formue
Enter your assets (cash, stocks, pension, home equity, other) and debt to get your net worth and liquid wealth. Each of the four key figures (assets, liquid wealth, debt, net worth) has a small line showing the last 12 months, green when it went the good way and red when not (for debt, rising is red). Save a dated månedsstatus to build a history (rows can be edited or deleted; each row shows the change since the previous one, and Bedste perioder lists the three biggest increases; År for år sums up each calendar year, and a dashed forecast on the history chart (can be switched off) continues the last 12 months' pace two years ahead; pointing at it shows the expected net worth for each month — all calculated on the fly, not stored) — or use Månedsstatus to save the same date into both the Formue history and the portfolio tracker in one go (on a phone it's guided, one field at a time: the date, each balance with last month's number filled in — Uændret or Ingen is one tap — a note and a summary; Hele skemaet switches to the full form) (afterwards a short message sums it up: how much net worth rose or fell since the last status, whether it's one of the year's three best months, and how many months in a row you've saved a status, with Se måneden opening Månedsoverblik on that month; monthlyStatusSummary in calc.js). A status can have a short note ("Bonus", "Købte bil", up to 60 characters): it's saved with the net worth point, shown as a diamond on the history chart with the note in its tooltip, in the history table (and its CSV export and import) and in Månedsoverblik for that period; "Ret" can change it, and saving the same date again keeps it. Typos are caught: a balance that becomes at least 5 times bigger or smaller than last time (and differs by at least 10.000 kr.), or drops to 0 from at least 10.000 kr., is flagged under the field ("et nul for meget?" when it's about 10, 100 or 1.000 times) and in an Er tallene rigtige? check before saving (suspiciousAmounts in calc.js) — see how the composition has changed over time, set your own goals (with the monthly saving needed to reach them by a deadline and whether your pace over the last year is enough), track milestones, and compare your net worth to other Danes of exactly your age using CEPOS's per-age table (2024 data at 2026 levels, pension counted after 40% tax, as CEPOS does). The full table opens with your age highlighted. Plus a light-hearted "your wealth equals n bananas / iPhones / Porsches" comparison. The emergency-fund bar runs from 0 to 9 months with the recommended 3–6 months marked, and Tilføj datapunkt folds away like in the portfolio tracker.
Everywhere
Every field has a small ? that explains it, and each tool has a foldable Hvad gør dette værktøj? box. Number fields accept simple arithmetic — type 12.500 + 3.200 or 450 * 12 and the result is filled in when you press Enter or leave the field. Danish (1.000, 2,5) and English (2.5) decimals both work, and the arrow keys still step the value.
Settings
Indstillinger in the menu opens a dialog: light or dark theme (follows the system by default), and a one-file JSON backup/restore of all Budget, Formue and Portefølje data. An optional reminder (on by default) appears around each month-end for people who track their numbers — from the last three days of a month to the 10th of the next — and opens Månedsstatus on the month's last day.
Kalender: Tilføj påmindelse til din kalender downloads an .ics file with a repeating event on the last day of every month at 19:00, so the monthly-status reminder arrives even when the site isn't open.
Skjul beløb: the eye button in the top bar blurs every amount on the page — key figures, tables, sentences with an amount in them and amount fields — so you can show the app to someone or use it in public. Percentages, dates and the shape of the charts stay visible; the charts lose their amount axis and tooltips. A field shows its number again while you type in it. The choice is remembered on the device (not in the backup file), and containsAmount in calc.js decides what counts as an amount.
Kodelås: an optional 4–6 digit code that hides the site when it's opened and after more than 5 minutes away, with Face ID or fingerprint where the device supports it (WebAuthn, no server). It's a screen lock, not encryption: the numbers stay readable in the browser, and only a salted PBKDF2 hash of the code is stored. A forgotten code can only be cleared by erasing the data on the device and restoring a backup. The lock stays on the device and isn't part of the backup file.
Design
The page is responsive: one layout that adapts to the space available rather than separate designs per device.
- Menu. A floating menu card on the left; below 900 px it becomes a menu button that slides the menu in from the left. On phones (below 640 px) a bottom bar replaces the menu button: Oversigt, a raised + Status for the monthly status, and Trackers, Værktøjer and Mere, which slide up sheets built from the menu card, so both menus always list the same items. A sheet closes with its ×, a tap outside it, Esc, or by dragging it down; a short drag springs back. The bar hides while you type, so it never sits on the keyboard.
- Stacking by available space. The tools, Budget and Formue use CSS container queries: when the content area (not the screen) is narrower than about 1150 px, the chart moves under the inputs, so it never gets squeezed next to the menu.
- Phones (below 640 px). Body text is about 14.5 px and small text never under 12 px, in line with Apple's and Material Design's type scales. Form fields stay at 16 px so iPhone doesn't zoom in. Cards are tighter (8 px apart, slightly smaller headings), charts have a landscape shape (roughly 4:3), long explanations are folded, and Tilføj datapunkt in Formue and Portefølje starts folded until you open it (then it's remembered).
- Themes. The light theme is forest green on warm off-white; the dark theme is black and greys with the same green and red.
- Explanations behind "?". Cards show their numbers; the text that explains them (a subtitle, a "Hvorfor …?" fold or a help text, marked
data-card-help in the HTML) sits behind a small "?" in the card's top-right corner and opens at the top of the card, like the "?" next to fields (js/card-help.js). Cards that are themselves an explanation, such as Om 4%-reglen and Regler og antagelser, stay as they are.
- Keyboard shortcuts (computer).
1–7 open the menu items in their order, N a new monthly status, B hides or shows amounts, ←/→ change month in Månedsoverblik and ? lists them all (js/shortcuts.js). They never fire while typing in a field, with a dialog or sheet open, behind the code lock, or together with Cmd/Ctrl/Alt, so a number typed into a field stays in the field and Cmd+1 still switches browser tabs.
All colours, spacing and radii are variables at the top of styles.css. The redesign (top bar, menu card, Oversigt, themes and phone adjustments) is the last part of the file, after the original component styles.
The optimal realisation strategy
For a regular depot, gains are only taxed when realised — at 27% up to a yearly threshold (79.400 kr. in 2026) and 42% above it. "Harvesting" means selling and immediately re-buying up to that threshold each year, so the gain is taxed at 27% now rather than partly at 42% later. But harvesting early also means paying tax earlier and losing compounding on it.
Rather than assume earlier is always better, the tool tries every possible year to start harvesting and picks the one that produces the highest final value. It then reports how much that beats never selling until the last year.
Running it locally
It is plain HTML, CSS and JavaScript with no build step. Serve the folder over HTTP rather than opening index.html directly, because localStorage behaves inconsistently on file:// URLs:
npm start
Then open http://localhost:4173. (npm start runs a tiny static server in scripts/serve.js with no dependencies; any static server works.) Chart.js and the fonts (Newsreader, Manrope and IBM Plex Mono) are part of the site in vendor/ and fonts/, so nothing is loaded from other servers and it works offline.
Tests
The financial calculations, the tax and lending rules, the percentile lookup and the Danish number/CSV parsers live in js/calc.js, which has no DOM dependencies and is tested with Node's built-in test runner — no packages to install.
npm test
Several tests pin exact known outputs (for example, 25 years at 8% from 100.000 kr. gives 496.847 kr. in a depot with harvesting from year 19), so any change to the maths is caught immediately. Browser tests in tests/e2e/ run the whole page in Chromium with Playwright. They check what unit tests can't see: that every section loads without JavaScript errors, that every chart exactly fills its box, that nothing scrolls sideways on a phone, and flows such as the budget dialog, the monthly-status overwrite warning, share links, syncing from a file, the menu, the settings dialog, the period picker and the foldable panels. tests/e2e/a11y.spec.js runs axe-core (the engine behind Lighthouse's accessibility audit) on every page, the dialogs, the privacy page and the phone's bottom menu, in both themes, and fails on any WCAG 2.1 A/AA problem such as low contrast, a missing label or something the keyboard can't reach.
npx playwright install chromium # once
npm run test:e2e
Both suites run automatically on every push and pull request via GitHub Actions; failing browser runs upload a trace you can open with npx playwright show-trace. Dependabot opens a pull request once a month when Playwright or the GitHub Actions have a new version, and the tests run on it like on any other.
The browser tests run on desktop Chrome, and the tests tagged @mobil also on an iPhone and iPad in WebKit (Safari's engine — it lays out grids differently from Chrome) and a small Android phone. They check for horizontal scroll, content cut off at a panel's edge, form fields under 16 px (iPhone zooms into those), that long explanations are folded on phones, that charts on phones are wider than they are tall, and that the overview puts its chart first on one-column screens — also after visiting another page and coming back. Install the browsers once with npx playwright install chromium webkit.
After changing CSS or JS, run npm run stamp. It gives styles.css and every js/ file in index.html a version stamp from the file's content (styles.css?v=42c619c5), so a new page never gets combined with an old, cached stylesheet or script. tests/assets.test.js fails if a stamp is out of date. The service worker also asks the server whether a file changed (cache: 'no-cache') instead of trusting the browser cache.
Project layout
index.html The whole UI (all tools are sections of one page)
privatliv.html Privacy page (Privatliv in the menu)
404.html Shown by GitHub Pages for addresses that don't exist (self-contained)
robots.txt, sitemap.xml For search engines (robots.txt only takes effect on a site's own domain)
SECURITY.md How to report a security problem, and what's by design
styles.css All styling: tokens (dark + light themes), layout, components, phone and print
js/calc.js Pure calculation logic - the only file the tests import
js/shared.js DOM helpers: slider/number binding, CSV download, chart colours and options
js/ui.js Dialogs, confirmations, undo toasts, foldable panels, history tables, Danish dates
js/field-help.js The "?" explanations next to each field
js/number-fields.js Number fields you can calculate in (12.500 + 3.200, 450 * 12)
js/fold.js Folds long explanations on phones
js/tool1-ask-akt.js ASK vs. Aktiedepot
js/tool2-monthly.js Aktiedepot with monthly contributions
js/tool3-fire.js FIRE calculator
js/tool4-portfolio.js Portfolio tracker
js/pension.js Pension
js/tax-tracker.js Skattegrænse (27 %-grænsen for aktieindkomst)
js/etf-tax.js Positive-list lookup in Tips & viden
data/positivliste.json Skattestyrelsens positive list (built by scripts/build-positivliste.py)
js/loan-capacity.js Hvor meget kan jeg låne?
js/buy-vs-rent.js Køb eller leje?
js/debt-payoff.js Gældsafvikling
js/monthly-status.js Månedsstatus (saves to both trackers)
js/share.js Shareable calculator links
js/budget.js Budget
js/net-worth.js Formue: net worth, history, milestones, comparison
js/month-overview.js Månedsoverblik: change per category for a month or a year
js/goals.js Formue goals
js/navigation.js Menu, sections and tools, page header, settings dialog, reminders
js/bottom-nav.js Bottom bar and sheets on phones
js/shortcuts.js Keyboard shortcuts on computers (1-7, N, B, ?)
js/card-help.js Card explanations behind a "?" in the corner
js/sync.js Backup file and syncing between devices (merge, not overwrite)
js/app-lock.js Kodelås: lock screen, code and Face ID / fingerprint
js/hide-amounts.js Skjul beløb: blurs amounts, chart axes and tooltips
js/update-check.js "En ny version er klar" with a reload button
js/feedback.js Feedback button and form (sent via Formspree)
js/pwa.js "Install as app" button; registers the service worker
js/report.js Printable one-page overview (Udskriv overblik)
js/overview.js Oversigt (start page)
js/overview-cards.js The key figures you can choose on Oversigt, and the chooser
sw.js Service worker: network first, cached copy offline
manifest.webmanifest App name, colours and icons
icons/ App icons: icon.svg is the source (the Newsreader O traced as outlines, so it needs no font);
the PNGs are rendered from it with scripts/render-icons.js
js/theme.js Theme switching and re-theming charts
fonts/ Newsreader, Manrope and IBM Plex Mono (woff2) with their OFL licences
vendor/ Chart.js 4.4.0 with its MIT licence (checked against cdnjs' published hash)
tests/calc.test.js Unit tests for calc.js
tests/assets.test.js Checks the version stamps, the app icons, the Chart.js file, and that nothing loads from other servers
scripts/stamp-assets.js Version-stamps styles.css and js/ in index.html and privatliv.html (npm run stamp)
scripts/serve.js Local static server for npm start and the browser tests (serves 404.html like GitHub Pages)
scripts/render-share-image.js Draws icons/share-image.png, the picture shown when a link is shared
tests/e2e/ Browser tests (Playwright), including accessibility checks with axe
Updating for a new tax year
Every yearly figure — ASK limit, 27%/42% threshold, tinglysning, PAL, pension limits, lending rules, interest deduction — sits in one block at the top of js/calc.js. The explanatory text on the page reads its numbers from that block (data-rule in the HTML), so a yearly update is: edit the block, adjust the tests that pin exact values, run npm test.
The positive list (Skattestyrelsens Liste over aktiebaserede investeringsselskaber) is published as an Excel file, usually updated during the year. To refresh data/positivliste.json, download the newest file from skat.dk and run:
python3 scripts/build-positivliste.py <file.xlsx> <year> <published-date>
It uses only Python's standard library and keeps the ISIN, name, tax residence and the first year each fund was registered.
Sharing a calculation
A link to Økonomis shows a preview in Messenger, iMessage, Slack, LinkedIn and the like: the title, a short description and icons/share-image.png (Open Graph tags in index.html and privatliv.html; redraw the image with node scripts/render-share-image.js).
Each calculator has a Del beregning button that copies a link reopening it with the same inputs. The inputs live after the # in the link, which browsers never send to a server. The trackers, budget and debt list can't be shared this way — they're personal data, and a link must never overwrite what someone has saved.
Syncing between devices
There's no server, so phone and computer share data through a file. Gem mine data saves everything in one JSON file — on a phone through the share sheet (Google Drive, iCloud Files, AirDrop), on a computer as a download. Hent data fra fil on the other device doesn't overwrite: planSync/applySync in calc.js merge the histories date by date, and where a part differs (budget, loans, goals …) the user picks which version to keep, with the most recently changed one suggested. To know what's newest, sync.js records when each part last changed (syncTimes, via a wrapper around localStorage.setItem that only stamps real changes). Parts that exist only on the device are kept, and the whole import can be undone.
Install as an app
The site is a Progressive Web App. In Chrome, Edge or on Android, Installér som app in the settings panel installs it; on iPhone/iPad it's Safari's Share → Add to Home Screen (the button explains this). The service worker (sw.js) fetches from the network first, so a new version is picked up as soon as you're online, and falls back to cached copies offline. On install it caches every file index.html refers to, so nothing needs updating when files are added. A page that stays open for a long time (the installed app is often kept alive in the background) checks for a newer version when you come back to it (at most every 10 minutes) and every 30 minutes while it's open: npm run stamp writes a version number for the whole page into <meta name="app-version">, and if the newest index.html has a different one, a message says En ny version er klar with a Genindlæs button (js/update-check.js). Note that on iOS the installed app has its own storage, separate from Safari — move data with Gem mine data / Hent data fra fil.
Privacy
Everything you enter stays in the browser's localStorage on your own device; there's no account, no cookies, no tracking and no ads, and the site loads nothing from other servers. The only thing ever sent is a feedback message, if you choose to write one. privatliv.html (Privatliv in the menu) explains this for visitors, including backup files, shared links, the code lock and hosting on GitHub Pages.
Feedback
Giv feedback in the menu opens a feedback form. Messages are sent to Formspree, which emails them on and keeps them in a dashboard. Only what the visitor writes is sent (plus which tool they were on) — never their budget or other numbers. The button is hidden until an endpoint is set: create a free form on formspree.io and put its address in FEEDBACK.endpoint at the top of js/feedback.js. The form shows a short privacy note (what is sent, to whom, and that messages are deleted within 12 months) — so delete messages older than 12 months in the Formspree dashboard, and delete a message sooner if someone asks.
Assumptions and disclaimer
- Tax rules reflect Danish law as of 2026: 17% flat ASK tax, 27%/42% progressive depot tax with a 79.400 kr. threshold, and a 174.200 kr. ASK deposit limit; 15.3% PAL tax; tinglysning of 1.850 kr. + 0.6% (deed) and 1.825 kr. + 1.25% (mortgage deeds); interest deduction of ~33% up to 50.000 kr. per adult and ~25% above. These figures are normally adjusted yearly and are not indexed in this tool.
- All projections assume a constant annual return. Real markets do not move in a straight line.
- The wealth comparison uses CEPOS's full table (one row per age, 18–90; 2024 data projected to 2026 levels, rounded to 1.000 kr.). Pension is counted after a notional 40% tax, as in CEPOS's figures, so the comparable net worth can be lower than the one shown in Formue. For curiosity only.
- This is a personal-finance calculator, not financial or tax advice. Consult a professional before making investment decisions.
License
© 2026 Simon Grynnerup Skouboe. All rights reserved — see LICENSE. You are welcome to use the website, but the code, design and text may not be copied, modified or redistributed without permission. Versions published before 24 September 2026 were MIT-licensed, and copies obtained under that license stay under it.
