roughlogic

Field math for the trades. Free, fast, no ads, no accounts, works offline.

roughlogic.com is 1709 small, single-purpose calculators for electricians, plumbers, HVAC techs, carpenters, restoration techs, firefighters, surveyors, and dozens of other trades. Everything runs in your browser. Every answer comes from a published formula and cites its source.

   

Use it

1. Search for what you need, or browse by trade.
2. Type your numbers. The answer updates as you type. There is no submit button.
3. Tap Copy to take a value with you.

Every field shows an example value as its placeholder, so you can see the expected unit and magnitude before you type over it.

Every calculator's page is the same four things, in this order:

Title + one line	what it does
Run the calculator	opens it with the example already loaded
Example	the exact inputs and the exact answer
Two collapsed blocks	the formula, source, and assumptions; and the scope and limits

Here is that Example block, from Voltage Drop:

You enter		You get
Phase	single	drop_V	7.45
Material	copper	percent	3.1
AWG	10
Length one-way (ft) length_ft	150
Current (A)	20
Source voltage (V)	240

Grounded in Vd = 2 · K · I · L / CM, NEC Ch. 9 conductor properties. Inputs are named the way the calculator names them, with the machine field name alongside when it differs; that name is what an AI agent passes.

Your inputs live in the URL, so a calculator is bookmarkable and shareable with its numbers preloaded. After the first load it works with no signal. No account, no email, no tracking, ever.

Use it from an AI agent

The whole catalog is available to AI agents (Claude Code, Claude Desktop, Cursor) through a local, zero-dependency MCP server that runs on your machine over stdio. No hosting, no network. Four tools (search_calculators, describe_calculator, run_calculator, run_calculators) read straight from this repo, so the agent surface can never drift from the site. See mcp/README.md.

What's in the catalog

21 trade benches. Search spans all of them at once; the letters are internal group codes (I is reserved).

	Bench		Bench
A	Electrical	N	Stage & Live Production
B	Plumbing & Gas	O	Kitchen & Food Service
C	HVAC	P	Field, Backcountry & SAR
D	Water Damage & Mold Restoration	Q	Historical Reference Data
E	Carpentry & Construction	R	Accounting, Tax & Small-Business
F	Fire-Ground Engineering	T	Bench Science & Laboratory Math
G	Cross-Trade Utilities	X	Real Estate
H	Knowledge References	Y	Educators & K-12
J	Trucking & Logistics	Z	Rigging & Heavy Lift
K	Mechanic - Auto, Marine, Aviation
L	Agriculture & Forestry
M	Water & Wastewater Operations

One calculator is one formula on one screen. (In the source and the gate names below, a calculator is called a tile.) Every formula is transcribed in docs/derivations.md and every citation in docs/data-sources.md.

Why you can trust the answers

The hard part of a calculator catalog is not the arithmetic. It is proving, at scale, that every tile stays correct as the catalog grows. That is a build problem here: npm run lint runs more than 30 static gates before a change can land.

Gate	What it guarantees
check-dimensions	every formula is dimensionally consistent
check-cross-validation	independent tiles computing the same quantity agree numerically
check-bounds	a fuzzer sweeps each tile's input domain; no NaN/∞, monotonicity where required
check-worked-examples	each tile's example reproduces a publisher-verified reference number
check-citation-coverage	every tile names a real, dated source, freshness-tracked
check-derivation-coverage	every formula has a written derivation
check-dead-inputs	no rendered field is silently ignored by the compute function
check-tile-contract	every tile is registered, crash-free, and matches its declared I/O shape
check-shell-mobile	zero horizontal scroll on every page at 320 px and 200% text zoom

CI adds four parallel jobs per push: lint + unit tests + data-integrity verification, Lighthouse (median of 3), axe-core accessibility at 320 px, and the full Playwright suite on Chromium and WebKit. At runtime, integrity.js re-verifies the SHA-256 of every data manifest against data/integrity.json; the read-only posture means the worst case is a visible warning, never silent corruption.

How it's built

A 100% client-side static site. No server, no database, no accounts, no analytics, no runtime third-party dependency.

The browser loads index.html + styles.css + app.js (router, search, theme, URL-hash state), which dynamic-imports one of 57 per-group calculator modules (calc-*.js) on first open, which reads the sharded JSON in data/. A service worker (sw.js) caches the shell and data shards keyed to the build hash, so the site works offline after the first load.

At build time only (never in production), build-data.mjs refreshes the integrity-hashed data shards from NIST, NOAA, NCEI WMM, FHFA, HUD, and published bulletins, and build-shells.mjs emits one zero-JS crawlable static shell per tile (1709) and per group, plus a sitemap that carries 1731 URLs.

The home payload gzips to well under the 100 KB budget. Opening a calculator dynamic-imports only that trade's module and only the data shards it needs. See docs/architecture.md and docs/seo.md.

Develop

npm install        # dev tooling only; the site itself has zero runtime deps
npm run dev        # serve the SPA locally
npm run build      # emit dist/ (SPA + static shells + sitemap)
npm run lint       # the full static-gate chain (30+ checks)
npm test           # unit tests (node --test)
npm run test:e2e   # Playwright integration suite (needs a browser)

The repo root holds the SPA entry (index.html, styles.css, app.js, sw.js), the calc-*.js modules, and shared UI helpers. data/ holds sharded JSON with per-folder manifests and integrity hashes. scripts/ holds build and gate tooling (never runs in production). specs/ is the numbered specification history; docs/ holds derivations, data sources, architecture, and the audit trail. See docs/maintainer-quickstart.md and docs/contributor-checklist.md.

License

MIT. See LICENSE.