Calcash

Know the net profit of every sale before you list it.

A free profit and pricing calculator for sellers on Mercado Livre, Shopee and Amazon Brazil — fees, taxes and shipping included.

---

Source branch with code: https://github.com/thaianramalho/Calcash (Contributor repo)

Why Calcash

Every marketplace charges differently: a commission that changes by category or price bracket, a fixed fee per item, shipping rules, plus the invoice tax (NF-e) you owe on each sale. Pricing by gut feeling is how sellers end up selling at a loss without noticing.

Calcash flips the question around. Instead of "how much will I make at this price?", you tell it the margin you want and it returns the price to list — and the profit you'll keep per sale.

• Free and unlimited — no sign-up, no login, no paywall.
• One calculator per marketplace, each applying that platform's own rules.
• Bilingual — Portuguese (Brazil) and English, picked automatically from the visitor's region.
• Fast, static, dark — a single-page React app with a polished dark UI and no backend required.

Features

Calculators

Marketplace	Route	What it models
Mercado Livre	/Calculadora	Classic / Premium commission (you enter the %), NF-e tax, selling expenses, seller-paid shipping, and the fixed per-unit cost on items under R$ 79 (≈ R$ 6.75).
Shopee	/CalculadoraShopee	The 2026 commission table, auto-detected by price bracket (commission % + fixed fee per item). No fee fields to fill in — it picks the right bracket for you and shows which one it applied.
Amazon Brazil	/CalculadoraAmazon	Category commission (you enter the %), NF-e tax, selling expenses, and DBA shipping estimated from price tier and product weight.

All three share the same pricing model:

price  = (product cost + selling expenses + fixed fees) / (1 − (tax % + commission % + margin %) / 100)
profit = price × margin %

Because the fixed fee can depend on the price itself (e.g. Shopee brackets, Mercado Livre's under-R$ 79 cost, Amazon's DBA tiers), the calculators resolve it iteratively until the price settles inside a consistent bracket.

Heads-up: marketplace fee tables change often and some vary by weight, dimensions or state of origin. Results are estimates — every calculator links to the official fee page, and Calcash is not a substitute for an accountant.

Home page

A dark, motion-driven landing page built around a small design system (see .claude/skills/frontend-design/SKILL.md):

• Hero — headline, CTAs and a glassmorphism preview of a worked example (R$ 50 cost, 8 % tax, 20 % fee, 15 % margin → list at R$ 87.72, keep R$ 13.16).
• Tools — one card per marketplace, straight into its calculator.
• Social proof — usage stats and seller quotes.
• FAQ — accessible accordion.
• Footer — closing call to action and contact links.

The navbar is fixed and scroll-aware (glass effect once you scroll), with a full-screen mobile menu.

Language and region switch

The site is fully translated into Portuguese (Brazil) and English.

1. First visit — the visitor's country is detected from their IP address. Brazil → Portuguese; anywhere else → English.
2. Manual override — the PT | EN switch in the navbar always wins, and the choice is remembered in localStorage.
3. Shareable links — append ?lang=en or ?lang=pt to any URL to force a language (and remember it).
4. Graceful fallbacks — if geolocation is unavailable, the browser's language is used. The UI never blocks on the network: it renders immediately with a best guess and corrects itself if the detected region disagrees.

Country detection tries, in order:

1. /api/region — a tiny Vercel serverless function that reads the x-vercel-ip-country header. First-party, no third party sees visitor IPs.
2. api.country.is — public fallback for hosts without that function (local dev, GitHub Pages, Docker).
3. navigator.language.

The detected country is cached, so the lookup runs once per visitor. <html lang>, the page title and the meta description follow the active language.

The calculators model Brazilian marketplaces, so amounts are always in Brazilian reais (R$), in both languages.

Getting started

Requirements: Node.js 16+ and npm.

git clone https://github.com/thaianramalho/Calcash.git
cd Calcash
npm install
npm start

The app runs at http://localhost:3000 (set PORT=3001 if that port is taken).

Command	What it does
npm start	Dev server with hot reload.
npm run build	Production build into build/.
npm test	Test runner (Create React App / Jest).

Build gotcha: CI platforms such as Vercel build with CI=true, and Create React App treats every ESLint warning as an error in that mode. Before pushing, verify with:

CI=true npm run build

(PowerShell: $env:CI="true"; npm run build)

Docker

docker build -t calcash .
docker run -p 3000:3000 calcash

Deploying

Calcash is a static single-page app and deploys anywhere that serves build/ with an SPA fallback to index.html. It is set up for Vercel, which also gives you real IP-based region detection through api/region.js. On other hosts, detection transparently falls back to the public geolocation API and then to the browser language.

Project structure

api/
  region.js                  Vercel function: visitor country from the edge header
public/
  img/                       Marketplace logos
src/
  i18n/
    pt.js · en.js            All user-facing copy, one dictionary per language
    index.js                 I18nProvider, useI18n(), region detection
    LangSwitch.js            PT | EN switch used by both navbars
  componentes/
    pagina-inicial/          Home page (composes the sections below)
    Navbar/ · Navbar2/       Home navbar · calculator-page navbar
    inicio/                  Hero
    ferramentas/             Marketplace cards
    prova-social/            Stats and quotes
    ajuda/                   FAQ
    footer/                  CTA + footer
    Calculadora/             Mercado Livre, Shopee and Amazon calculators
      CalcParts.js           Shared field, title, buttons and result cards
  lib/                       Motion presets and the scroll-reveal helper
  styles/tokens.css          Design tokens (colors, type scale, 8px grid)

Contributing

Edit copy or add a language

All text lives in src/i18n/. To change wording, edit pt.js and en.js (keep both files on the same key structure). To add a language, create a new dictionary with that structure, register it in DICTIONARIES in src/i18n/index.js, and add a button to LangSwitch.js.

Update a marketplace's fees

Fee logic sits at the top of each calculator in src/componentes/Calculadora/:

• Shopee — the FAIXAS_SHOPEE bracket table.
• Amazon — the freteAmazon() function (DBA tiers).
• Mercado Livre — the under-R$ 79 fixed cost inside calcular().

If you change a table, update the matching disclaimer in the dictionaries so users know which year the numbers come from.

Design

Before touching the UI, read the design system in .claude/skills/frontend-design/SKILL.md and reuse the tokens in src/styles/tokens.css rather than hard-coding colors or spacing.

Roadmap and known gaps

• The usage stats and seller quotes in the social-proof section are placeholder content — replace them with real data before launch.
• Mercado Livre and Amazon commissions are entered manually (they vary by category); a category picker would remove that step.
• An experimental Mercado Livre listing lookup (/BuscarAnuncio) is routed but not linked from the UI, and it is not translated.
• No automated tests yet for the pricing formulas.

Disclaimer

Calcash is an independent project and is not affiliated with Mercado Livre, Shopee or Amazon. Marketplace names and logos belong to their respective owners. Figures are estimates for pricing guidance only.

License

ISC — see package.json.