Unit Converters: Free, Private, No Tracking
Fourteen converters covering the physical quantities that come up in everyday life and technical work. Each one includes the conversion factors used, worked examples, and the specific traps that quantity is known for. Everything runs in your browser, nothing is sent to a server.
Length, Area & Volume
Weight & Temperature
Speed & Acceleration
Pressure, Force & Torque
Energy & Power
Data, Angle & Frequency
How the converters work
All fourteen share the same approach. Rather than storing a separate factor for every possible pair of units, each unit is defined by its relationship to one base unit for that quantity: the meter for length, the gram for weight, the pascal for pressure. A conversion then takes two steps, from the source unit into the base unit, and from the base unit into the target.
This has a practical benefit beyond simplicity: rounding happens once at the end rather than accumulating through a chain of intermediate steps.
Temperature is the exception. Celsius, Fahrenheit, and Kelvin do not share a zero point, so conversion requires an offset as well as a factor. That is also why a temperature difference converts differently from a temperature itself, a distinction the temperature converter explains in detail.
Which converter for which task
| Task | Converter |
|---|---|
| US height in feet and inches to centimetres | Length |
| Apartment size between m² and ft² | Area |
| US recipe cups to millilitres | Volume |
| Body weight between kg, pounds, and stone | Weight |
| Oven temperature between °C and °F | Temperature |
| Speed limits between km/h and mph | Speed |
| Tire pressure between bar and PSI | Pressure |
| Electricity and nutrition energy figures | Energy |
| Engine output between kW, hp, and PS | Power |
| Why a 1 TB drive shows as 931 GB | Data size |
| Degrees to radians for programming | Angle |
| Engine RPM to hertz | Frequency |
| Bolt torque between N·m and ft·lb | Force and torque |
| 0 to 100 km/h expressed in g-force | Acceleration |
About accuracy
A common assumption is that converting between metric and imperial units always introduces error, because the factors look like awkward decimals. That has not been true since 1959, when the International Yard and Pound Agreement fixed the yard at exactly 0.9144 meters and the pound at exactly 0.45359237 kilograms.
So 1 inch = 2.54 cm is a definition rather than a rounded approximation, and the same applies to feet, miles, ounces, and pounds. Where a factor genuinely is approximate, such as Mach numbers, which depend on air temperature, or CMYK colour values, which depend on the printing device, the relevant page says so explicitly.
Results are shown with up to 10 significant digits with trailing zeros removed. For most practical purposes far fewer digits are appropriate: carrying more precision than your original measurement justifies creates false confidence rather than accuracy.
Related
- Developer tools, 18 tools for Base64, JSON, hashing, RegEx, and more
- Portal home