Length Converter
Convert between metric and imperial length units. e.g. “How many inches is 30 centimetres?”
Enter your values
Results update as you type. All calculation happens in your browser.
Methodology
Convert between metric and imperial length units. This tool uses a standard, documented formula and runs entirely on your device.
Last reviewed January 2026 · Runs client-side
Related calculators
Converting between metric and imperial length
Length conversions come up constantly, reading a recipe, following instructions written for another country, or checking a measurement against a spec. The safe way to convert between any two units is to route through a common base, and this tool uses metres.
Because every unit here has an exact factor relative to the metre, conversions are precise rather than approximate, and the tool shows the factor it used so you can verify the result.
How to use this calculator
- Enter the value you want to convert.
- Choose the unit you're converting from and the unit you're converting to.
- Read the result and the conversion factor.
What the inputs mean
- Value
- The number to convert.
- From / To
- Any supported metric or imperial length unit.
30 centimetres converts to about 11.811 inches, using the exact factor of 1 inch = 2.54 cm.
The formula, in plain terms
Result = value × (from-unit in metres) / (to-unit in metres). Every unit is defined by an exact factor relative to one metre.
Good to know
- 1 inch is exactly 2.54 cm, most other imperial-metric factors derive from that.
- For very large or small values, keep an eye on the number of decimal places you need.
Frequently asked questions
Are these conversions exact?
The metric-imperial factors used here are the internationally defined exact values, so results are as precise as your input.
Last reviewed January 2026. This explainer is general information, not professional advice.