Reproducible
Same input, same result. No randomness, no hidden rounding — the rules are public and the math is fixed.
About
Calculators you can audit
centav.io is a free set of browser-based financial calculators. Every result shows its formula, cites an official source, and carries a visible update date — so you can check the math yourself, with nothing you type ever sent to a server.
3 tools on the roadmap
100% in your browser, no sign-up
$0 cost to use
Mission
Retire the fragile spreadsheet and the black-box calculator. Each centav.io tool runs in your browser, shows the formula, and cites the source of the rule. Everyday money — price, deadlines, interest — should never depend on trusting a result you can't see.
Vision
A financial tool the reader never has to take on faith. We want every calculation on centav.io to be something you can follow line by line, reproduce in your own spreadsheet, and trace back to the official rule behind it.
Principles
Private
Calculations happen in your browser. Nothing you type is sent to a server.
Sourced
Tax and financial rules cite the official body and the date we checked them.
Free
No subscription, no paywall. The tools are open to everyone.
What we commit to
Human-reviewed translations
Content is born in three languages and reviewed by a person before it goes live — never machine-translated in bulk.
The method stays open
Every tool shows the formula and defines its variables. If a rule changes, we update the tool and the date, and show what changed.
Official sources only
We cite Receita Federal, Banco Central (BCB) and ANBIMA — never an anonymous source for a rule about your money.
Built to be usable
Fast, accessible (WCAG AA) and readable on any device, because a tool you can't reach is a tool you can't trust.
A transparent method
Money is handled in whole cents; dates in UTC. Formulas follow public rules, and every page shows the author, the reviewer and the update date.
When a rule changes, we update the tool and the date — and you see exactly what changed.
Who's behind it
centav.io is built and maintained by the centav.io team. The same people sign every tool, cite the sources behind each rule, and keep the update dates honest. Questions about a calculation? Talk to us.
Start with the markup calculator
Cost, markup and the equivalent margin, the instant you type.