A free suite of 77 financial, investment, loan, retirement, and stock calculators.
🔗 Live: https://kakoucalc.serverkakoulabs.org
KakouCalc is a fast, static, privacy-friendly calculator site. Every calculation runs entirely in the visitor's browser — no accounts, no data collection — and every calculator ships as a real, server-rendered page with a genuine worked example, so it's useful before a single line of JavaScript runs.
- 77 calculators across 7 categories: Finance & Investment, Loan & Mortgage, Retirement, Stock, Credit Card, Auto Loan & Lease, and Miscellaneous.
- Static & multi-page — one real, crawlable URL per calculator (
/calc/<id>), each prerendered with a real computed example (not a$0.00shell). - Editorial layer — hand-written guides (formula, worked example, key terms, FAQ) on the deepest-covered calculators, plus an auto-generated How to use + Worked example on every page, derived from each tool's real fields and the engine's own numbers.
- Independently verified math — a standalone suite recomputes every calculator from
first principles and checks every quoted example figure (
scripts/verify-math.mjs). - Embeddable widgets — each calculator has an
/embed/<id>iframe version for other sites, with attribution links back to KakouCalc. - Blog + trust pages — explainer articles, plus About, Methodology, Privacy, Terms, and Contact.
- Privacy-first — calculations never leave the browser; the site's own code runs no
analytics and sets no cookies (only a light light/dark theme preference in
localStorage).
- Astro — static site generator (
output: "static") - Dependency-light: no UI framework; result charts are hand-rolled inline SVG
- Cloudflare Pages — hosting and CI builds
- Node 22 (see
.nvmrc)
Prerequisites: Node.js 20+ (22 recommended) and npm.
npm install # install dependencies
npm run dev # dev server at http://localhost:4321
npm run build # production build → dist/ (refreshes FX/CPI first)
npm run build:offline # build using committed data, no network fetch
npm run preview # preview the production build locally
node scripts/verify-math.mjs # run the math verification suiteAbsolute URLs (canonical, sitemap, Open Graph) come from SITE_URL. Set it when
building outside Cloudflare so they don't fall back to localhost:
$env:SITE_URL="https://kakoucalc.serverkakoulabs.org"; npm run buildOn Cloudflare Pages, SITE_URL is an environment variable (with CF_PAGES_URL as a
fallback).
src/
pages/ Routes: index, calc/[id], embed/[id], blog, about, methodology,
privacy, terms, contact, 404, robots.txt
layouts/ Base.astro — shared <head>, header, sidebar, footer
lib/ calculators.js the DOM-free calculation engine (all 77 tools)
render.js form + result HTML builders (build- and client-side)
explain.js auto-generated How-to-use + worked example
charts.js inline-SVG result charts
display.js label helpers
data/ site.js identity / editorial constants
guides.js hand-written full guides
explainers.js hand-written formula + key terms + FAQ (added in batches)
examples.js realistic example inputs, one set per calculator
articles.js blog posts
reference.json FX / CPI data, refreshed at build time
scripts/ client-side calculator + UI behavior
styles/ global.css
scripts/ fetch-data.mjs refresh FX/CPI at build time
verify-math.mjs independent math verification
gen-og-image.mjs social-card generator
public/ static assets (favicon.svg, og-image.png)
- A new calculator — add its definition (fields +
compute()) tosrc/lib/calculators.js; a real/calc/<id>page, an/embed/<id>widget, and a sitemap entry all fall out automatically. Add a realistic example tosrc/data/examples.js. - A guide, or formula/FAQ depth — add an entry to
src/data/guides.js(full guide) orsrc/data/explainers.js(formula + terms + FAQ). Every figure quoted must match the engine —verify-math.mjsenforces it. - A blog post — add to
src/data/articles.js.
Static build deployed to Cloudflare Pages (Git-connected): build command
npm run build, output directory dist. See DEPLOY.md for the full
deployment guide, the daily data-refresh setup, and the reasoning behind the
architecture.
KakouCalc is for education and general information only — not financial, investment, tax, or legal advice. Results are estimates based on the inputs you provide. See the methodology page for how the tools are built and verified.
Personal project. The source is provided as-is and is not currently released under an
open-source license — please don't republish the content or code wholesale. (Add a
LICENSE file to change this.)