Ultimate Calculator
A fast, modern, privacy-friendly all-in-one calculator for everyday calculations. Built as a lightweight client-side web app with a responsive interface that works on desktop and mobile.
Live: https://uc.kampaxis.com
Features
Calculator
- Standard arithmetic with operator precedence and brackets
- Calculator-style percentages
- Change sign (±): hold − on the keypad, or F9 on a keyboard
- Decimal and negative number support
- Calculation history
- Results show up to 10 decimals when the screen has room (6 on a narrow phone); copying copies what you see
- Copy results
- Keyboard support
- Works offline once opened: the app keeps a copy on the device and updates it when online
- Step-by-step explanations of how a result was worked out
- Brackets that change nothing are tidied away; C clears the number being typed, AC everything
- Memory keys: MC, MR, M+, M−, MS (Ctrl+L, R, P, Q, M on a keyboard), kept after the app is closed
- ⋯ opens every function and constant by group, with a search
Scientific
- The f(x) switch on the calculator's display adds scientific keys: sin, cos, tan and their inverses, ln, log, powers, roots, 1/x, x!, π, e and EE
- Degrees or radians; exact answers wherever they are exact (2¹⁰, √(9/4), sin 30°)
- Functions apply to the number just typed or to the result: 30 then sin gives sin(30)
- Hyperbolic functions and their inverses, cot, sec, csc, |x|, nCr, nPr and mod; π, e, φ and 41 physical constants (CODATA 2018) with a search
- Complex numbers: i, polar entry (2∠30), exact arithmetic, every function, results in both forms at once (a + bi with r∠θ under it, live while typing)
Unit Converter
- Length, area (including stremma), mass, volume, speed, time, data, energy, power, pressure, angle and temperature conversions
- Calculator-style arithmetic directly inside unit fields
- Expressions can be chained just like the main calculator
- Percentage calculations
- Automatic conversion while entering an expression
- Switch conversion direction
- Keypad-based input designed for a calculator-like experience
Graph
- Plot up to three functions of x
- Roots, minima, maxima and intersections are marked
- Pan, zoom, fit to the curve and save the graph as an image
Dedicated Calculators
- Fuel cost calculator
- Electricity/energy cost calculator: from a device's power and hours, or from kWh you already know (a bill or meter)
- VAT add/remove calculator (VAT rounded to cents, as on invoices)
- Percent: a percentage of a number (12% of 540), price after a discount, % change between two values, and a tip calculator that splits the bill between people
- Dates: days between two dates and a date plus or minus days, picked with the device's own calendar; all days or working days only (Greek public holidays)
- Currency: the European Central Bank's daily rates for about 30 currencies, with calculations inside the values; works offline with the last rates
- Subnet (IPv4): network, broadcast, host range, mask and wildcard from an address and a prefix or mask, and the smallest subnet for a number of hosts
- Interest: a loan's monthly payment and total interest, how long a loan takes with the payment you can afford, and what savings grow to with monthly deposits, with charts
- Numbers: GCD and LCM of two or three numbers, prime factors and divisors of numbers up to 15 digits
- Equations: ax² + bx + c = 0 with real or complex roots (exact, x = −1 ± √2), and a system of two equations
- Programmer: a whole number (up to 64 bits) in decimal, hexadecimal, binary and octal at once, with the working
- Statistics: average, median, standard deviation (sample s and population σ), min, max and sum of a list of numbers, typed one at a time or pasted
- Charts and step-by-step explanations for every tool
- Each mode keeps its own History; AC clears the values
Interface
- Responsive desktop and mobile layouts, in portrait and landscape (keypad beside the display when a phone is turned sideways)
- Themes: Light, Paper, Dark, Black (true black for OLED screens), your own light and dark themes, or Match device
- English and Greek language support
- Installable on phones: an install button opens the install dialog on Android, and shows a short Add to Home Screen guide on iPhone
- Mobile-friendly calculator controls
- One-tap mode tabs for the pinned modes; every mode (Calculator, Units, Currency, Graph, VAT, Percent, Interest, Dates, Fuel, Energy, Subnet, Programmer, Numbers, Equations, Statistics) is in All modes (⊞, at the top), with a search, pins, and an All | Default | None switch to pin every mode, the starting four or none at once; Alt+1–9 for the first nine on a keyboard
- On big screens History sits on the left and the working on the right, beside the calculator, updating live
- Calculation explanations presented in a readable step-by-step view
- Tips for every mode, with keyboard shortcuts on computers, from the footer (or ? on a keyboard)
Author
Leonidas Kampaxis (Λεωνίδας Κάμπαξης)
Technology
Ultimate Calculator is intentionally lightweight: plain HTML, CSS and vanilla JavaScript, with no framework and no backend. There is nothing to build while editing: public/ runs as it is; the deploy joins and minifies the scripts (tools/build.mjs) so the first visit loads faster. Calculations happen in the browser, and history and settings are stored in the browser (localStorage). There are no accounts and nothing is sent to a server.
public/ the website, exactly as it is served
index.html page shell
styles.css all styles and themes
js/ the app, one file per area (calculator, units, tools, graph, history, ...)
manifest.webmanifest, icons
tests/test_app.py browser tests (Playwright)
tools/bump-version.py sets the version everywhere it appears
tools/build.mjs the deploy build: public/ with the scripts joined and minified (esbuild, package.json)
Dockerfile, nginx.conf the Docker image: nginx serving the built public/
docker-compose.yml for running the image yourself
The scripts in public/js/ are plain scripts that share globals, loaded in a fixed order by index.html. CLAUDE.md describes what each one contains; how the code works is in docs/claude/ (one file per part of the app).
Run locally
It is a static site, so any static web server works:
python3 -m http.server 8080 -d public
or with Docker:
docker build -t ultimate-calculator .
docker run --rm -p 8080:80 ultimate-calculator
Then open http://localhost:8080.
Tests
pip install playwright && python3 -m playwright install chromium # once
python3 tests/test_app.py
# the deployed version instead (GitHub tests this one):
npm ci && node tools/build.mjs && python3 tests/test_app.py --site build
The tests open the app in Chromium at desktop and phone sizes, in both languages and themes, and check the calculator, brackets, Units, the tools, History, the mode tabs, the language switch and that nothing is cut off on phones.
Deployment
Every push to main runs one GitHub Actions workflow (.github/workflows/deploy.yml): it builds the site (node tools/build.mjs: the ~26 scripts become one minified js/app.js, styles.css is minified), tests that build, and only if the tests pass publishes it to
- GitHub Pages – the site at https://uc.kampaxis.com
- Docker image –
ghcr.io/leothegreat777/ultimate-calculator:latest, tested before it is published. To update a self-hosted copy: docker compose pull && docker compose up -d.
If the tests fail, nothing is deployed and the live site stays as it was. If two pushes land within seconds of each other, the older run is cancelled and only the newest one deploys.
Versioning and changelog
Versions follow MAJOR.MINOR.PATCH: a new feature raises the middle number, a fix the last one; the version shows
in the app's footer. What changed in each version is in CHANGELOG.md.
python3 tools/bump-version.py patch|minor|major sets the version everywhere and starts its changelog section.
Project Direction
The goal is to turn Ultimate Calculator into a single calculation interface for as many everyday calculations as possible, while keeping the core experience fast, simple and independent of AI or a backend.
The project is actively evolving. The interface, calculation modes and conversion system are being refined continuously with a strong focus on making the app feel like a polished native calculator rather than a collection of separate web forms.
Roadmap
Ideas for later:
- More unit categories and conversions
- Markup and margins
- Reusable formulas
- More dedicated calculators
- Additional languages
- Continued accessibility and interaction improvements
Self-hosting
The application is designed to be easy to self-host. It is a static site (the public/ folder), so it runs on GitHub Pages, behind Nginx or any static web server, or from the Docker image, with no database or application backend.
