CalcBoard / Free Calculators

Free Online Calculators

Six calculators that run in your browser, free, with no ads, no sign-up, and nothing sent to a server. Built by the people behind the CalcBoard app.

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Each of these does one job properly and shows its working. Nothing here is a teaser for the app — they are complete, and they are free.

Percentage Calculator

Percent of, percent change, add or subtract a percentage — with the formula shown.

Tip & Bill Split Calculator

Tip, total, and per-person split, plus a round-up suggestion.

Discount Calculator

Sale price, savings, stacked discounts, and tax.

Unit Price Comparison

Compare two or three package sizes and find the real better deal.

Hex, Binary & Octal Converter

Decimal, hex, octal, and binary at once, plus bitwise operations.

Loan Comparison Calculator

Two loans side by side: monthly payment and total interest.

All Unit Converters

Ten unit converters covering 79 units, from length to pressure.

Why we built these

CalcBoard exists because one calculator holding one number is not how people actually work. You compare two prices, check a total against a receipt, or convert a measurement and then use it in a formula. Every tool above is a small version of that idea — and the pattern they all run into is the same: sooner or later you need two of them at the same time.

That is what the app does. Up to eight independent calculators on one screen, each in basic, scientific, programmer, or unit-converter mode, with results passed between them. Free for two panels, no ads in any version.

Four things the app does that a web page cannot

  • Works with no connection. A web tool needs a signal; the app runs on airplane mode, in a basement, or in a supermarket aisle.
  • Exact decimal arithmetic. Every web calculator, this one included, computes in floating point and can round on the last digit. The app doesn't — 0.1 + 0.2 is exactly 0.3, so money totals reconcile to the cent.
  • Remembers your work. History, bookmarks, labels, and named variables that persist between sessions.
  • Several at once. Up to eight calculators on one screen, passing values between them.
Privacy: these tools run entirely in your browser. There is no analytics script, no cookie, and no third-party JavaScript on this site — nothing you type here reaches us or anyone else.

Frequently Asked Questions

Are these tools really free?
Yes — no ads, no sign-up, no usage limits, and no upsell wall. They are complete tools, not demos.
Do you track what I calculate?
No. Every tool computes in your browser with inline JavaScript. The site loads no analytics, no cookies, and no third-party scripts, so nothing you type leaves your device.
Do I need the app to use these?
No. The app is for when you want the same maths offline, with exact decimal precision, history, and several calculators on screen at once — but every tool on this page works on its own.
Why is the app more accurate than the web tools?
Browsers compute with IEEE-754 floating-point numbers, which cannot represent values like 0.1 exactly. CalcBoard uses arbitrary-precision decimal arithmetic instead, so money and measurement sums come out exact.

Run several of these at once

CalcBoard puts up to 8 calculators on one screen, offline, with exact decimal maths. Free to download.

Download Free on App Store

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