Unit Converter Guide

How to choose units, convert measurements and avoid common conversion mistakes.

Unit conversion is the process of expressing the same quantity using a different measurement unit. The quantity itself does not change; only the numerical representation changes. This distinction is especially important when switching between metric and imperial units.

Start by identifying the quantity

Length, mass, temperature, area, volume and data storage each have their own conversion relationships. Do not use a length conversion factor for an area measurement, for example, because area is two-dimensional.

Metric conversions

Metric units are usually related by powers of ten. Moving from metres to centimetres multiplies the numerical value by 100 because a metre contains 100 centimetres. Moving from metres to kilometres divides the numerical value by 1,000.

Temperature is different

Temperature conversions generally involve an offset as well as a scale factor. That is why Celsius to Fahrenheit cannot be handled by a simple multiplication alone.

Area and volume need special care

When a length unit is squared for area, the conversion factor is squared. When it is cubed for volume, the factor is cubed. This is a common source of surprisingly large errors.

Use the converter

The Unit Converter provides common measurement categories in one place. For engineering, construction or regulated work, confirm critical measurements against the specification or authoritative reference.