Length Converter
Convert metric, imperial, and astronomical length units with reliable base factors.
Base factors at a glance
Every value is normalized to metres first. Exact relationships include 1 inch = 0.0254 m, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1,609.344 m, and 1 nautical mile = 1,852 m. One astronomical unit equals 149,597,870,700 m.
How to convert a length
- Enter the measured or planned length.
- Select its source unit.
- Select the target unit you need.
- Use the swap button to reverse the same relationship.
Example: metres to feet
Dividing 100 m by 0.3048 m per foot gives 328.0839895 ft. For a rough distance, 328.08 ft is sensible; for technical work, rounding should reflect the precision of the original 100 m measurement.
Unit accuracy is not measurement accuracy
Conversion factors are reliable, but they cannot improve an imprecise input. Thermal expansion, instrument error, and object tolerances are not considered. Scientific notation keeps extreme results from appearing incorrectly as zero.
Frequently Asked Questions
How do I convert inches to centimetres?
Multiply inches by 2.54. The factor is exact: one inch equals exactly 2.54 centimetres.
How many feet are in a metre?
One metre is approximately 3.28084 feet. In the reverse direction, one foot is exactly 0.3048 metres.
How are a mile and a nautical mile different?
A statute mile is exactly 1,609.344 metres. A nautical mile is longer at exactly 1,852 metres and is mainly used for navigation.
Why do conversions produce long decimals?
Many units are not whole-number multiples of one another. The converter keeps the unrounded value internally and rounds only the display.
How many decimal places should I use?
Round to match the precision of the original measurement. If your input is accurate only to a centimetre, extra displayed decimals do not make it more accurate.
Can I convert very small and very large lengths?
Yes. Nanometres and micrometres cover small scales, while astronomical units and light-years cover large distances. Extremely small or large results use scientific notation.