Factorio Calculator

A production-rate calculator for Factorio 2.0 and Space Age: pick what you want to make and how fast, and it works out every machine, belt and input behind it.

Use it: https://factoriocalculator.app/

It is a fork of Kirk McDonald's Factorio Calculator (source, Apache-2.0). The solver and data model are his; the page around them is new:

• Table first. One row per item, grouped Build here / Bring in from another build / Mine or pipe in. Open a row for what it needs, where it goes, machine ratios ("1 offshore pump feeds 9.6 foundries"), the recipe and the machine, per row or for the whole build.
• Graph. The same plan as a left-to-right flow. Every item's lines have their own colour and dash pattern. Hover or click a card and each of its lines says its rate, belts ("1 1/3 belts") and how many machines on each end it takes ("32 of 56 send this").
• Colour-blind mode (Settings > Display) writes the colour on belt, splitter and inserter icons.
• Nickname search ("red science 60, gears, blue chip 45"), a scratch pad, and the whole plan in the link, so a link is the plan.

Running it locally

It is a Svelte 5 + Vite app that builds to static files:

npm ci
npm run dev        # http://localhost:5173/calc.html, with hot reload
npm run build      # the site, prerendered, in dist/
npm run preview    # serve dist/ on http://127.0.0.1:8000/calc.html

src/components/ holds the Svelte components and src/lib/ the solver plus the UI modules still being moved to components. public/ (data, images, the changelog) is served as-is. The code rules are in CLAUDE.md.

This repo is also the calculator inside the Factorio Companion (a Claude Desktop MCP server), whose local server adds extras the static site hides: reading settings from your save and adding a plan to a board.

Tests

tests/e2e/ is a Playwright suite that pins down what the page does: the plan it works out for a link, what every control changes, the link it writes back and how each state looks. It drives the page only as a player would and reads back what the page shows, so it is the check that a rewrite (to a framework, say) still behaves the same.

npm ci
npx playwright install chromium
npm test                      # build, then the whole suite against dist/
npx playwright test golden    # one spec file, by name
npm run test:update           # refresh snapshots after an intended change
npm run test:ui               # watch and debug

• tests/e2e/support/ holds the only code that knows the markup: selectors.ts (core hooks), areas/*.ts (per-feature hooks), calculator.ts (the page object). A rewrite that changes the markup updates those files, and every spec should then pass unchanged.
• specs/golden.spec.ts holds 45 plans across every dataset. Each plan's table, footer, graph and written link are compared with JSON snapshots in __snapshots__/golden.spec.ts/, and each link must reopen to the same plan.
• specs/visual.spec.ts compares screenshots with the PNGs in __snapshots__/visual.spec.ts/. They are rendered on Linux Chromium with the vendored Titillium Web, so refresh them on the machine (or CI) that runs the gate.
• Every test fails on any page or console error, and nothing is fetched from outside the site. The Google Fonts requests are answered from tests/e2e/fixtures/fonts/.
• CI (.github/workflows/test.yml) runs the suite on every pull request and branch push. On main, deploy.yml runs it first and publishes the site only when it passes. To regenerate snapshots on the CI machine, run the Test workflow by hand with "update snapshots" ticked, then download the snapshots artifact.
• To run the suite against another build, set CALC_BASE_URL to its address and CALC_PAGE to the page path (default /calc.html).

Licence

Apache-2.0, as upstream: see LICENSE and NOTICE-factorio-companion.md. Factorio's item and machine icons are Wube Software's.