Online Calculator & Converter: free calculators and unit converters

About these tools

Every converter here works from exact unit definitions. Imperial lengths are defined in metric terms — an inch is exactly 2.54 cm and a foot exactly 0.3048 m — so converting between them introduces no approximation beyond display rounding.

Each calculator page shows the formula it uses, a worked example and its limitations, so you can check the result yourself. Construction tools never assume product coverage; enter the values printed on your materials.