CalcBoard / Unit Converters

Free Unit Converters

Ten converters covering 79 units, free in your browser with no ads and no sign-up — and all of them offline in the CalcBoard app.

Download CalcBoard Free

Every converter below uses the same factor table as the CalcBoard app, exported straight from the app’s source so the web and the app never disagree. Pick a category:

Length Converter

Miles, kilometres, feet, inches, yards, nautical miles.

Weight Converter

Kilograms, pounds, ounces, grams, stone, metric tons.

Temperature Converter

Celsius, Fahrenheit, Kelvin — with the formulas.

Volume Converter

Litres, US and UK gallons, cups, quarts, spoons.

Area Converter

Acres, hectares, square feet, square metres.

Speed Converter

mph, km/h, knots, metres per second.

Data Storage Converter

GB vs GiB, bytes through petabytes.

Time Converter

Milliseconds through years, assumptions stated.

Energy Converter

Joules, calories, kWh, BTU.

Pressure Converter

PSI, bar, kPa, atmospheres, mmHg.

Why another set of converters?

Because most of them are covered in ads, and because the numbers behind them are rarely shown. Every page here lists the exact factor each unit uses to reach its base unit — the same constants the app computes with — so you can check the arithmetic rather than trust it.

One difference worth knowing: like every web calculator, these browser tools compute in ordinary JavaScript numbers, so very long results round on the last digit. The CalcBoard app's converter uses exact decimal arithmetic instead, and works with no connection at all.

What the app adds

  • Offline, always. All 79 units work on a plane, in a basement, or on airplane mode.
  • Conversion next to calculation. Convert in one panel while a second panel runs the formula that uses the result — that is the whole point of a multi-panel calculator.
  • Exact decimal maths. No floating-point drift on the last digit.
  • Free tier: length, weight, and temperature (13 units). The one-time $2.99 Premium unlock adds the other seven categories.
No currency conversion. CalcBoard converts physical and digital units only — there are no exchange rates in the app or on this site. If you need currency, use a tool that updates rates daily.

Frequently Asked Questions

Are these converters free?
Completely. No ads, no sign-up, no limits, and nothing is sent to a server — the arithmetic happens in your browser.
Do the web converters match the app exactly?
The factors are identical — they are exported from the app's source code. The arithmetic differs slightly: the browser uses standard floating-point numbers, while the app uses exact decimal arithmetic, so the app is the more precise of the two on very long results.
Does CalcBoard convert currency?
No. The converter covers ten physical and digital categories — length, mass, temperature, area, speed, time, data, volume, energy, and pressure. Currency exchange needs live rates, which CalcBoard does not fetch.
How many units does the app convert?
79 units across 10 categories. 13 of them — length, weight, and temperature — are free; the rest come with the one-time $2.99 Premium unlock.

Take all 79 units offline

CalcBoard converts units next to a live calculator, with no connection required.

Download Free on App Store

Keep exploring