Units tool

Length converter

Metric, imperial and nautical, converted through a single base unit so error never accumulates.

Nothing you type is sent anywhere. This runs entirely in your browser — no upload, no server round-trip.

From

Decimal places

Common conversions

1 inch	= 2.54 cm
1 foot	= 0.3048 m (30.48 cm)
1 yard	= 0.9144 m
1 mile	= 1.609344 km
1 kilometre	= 0.621371 mi
1 metre	= 3.28084 ft
1 centimetre	= 0.393701 in
1 nautical mile	= 1.852 km (1.15078 mi)

How to use it

1

Pick your units

Choose the unit you have on the left, and the unit you want on the right.
2

Type a value

Enter a number in either box — the other updates instantly. Edit the result field and it converts backwards too.
3

Swap or adjust precision

Use the swap button to flip direction, or the decimal-places control if you need a rounder or more exact answer.

Questions people ask

Why does my answer have so many decimal places?

The converter shows up to the number of decimal places set in "Precision" — 6 by default. Lower it if you want a rounder number; the underlying value is always computed at full floating-point precision first, so lowering precision only changes the display, not the accuracy of the conversion.

Which nautical mile does this use?

The international nautical mile, defined as exactly 1,852 metres. This is the modern standard used in aviation and shipping worldwide, not the older UK Admiralty mile (6,080 ft) which some historical documents use.

Why do I sometimes see a number like 0.30000000000000004 in other converters?

That is a floating-point rounding artefact from how computers store decimal numbers in binary — it happens in almost any calculator, not just length converters. This tool formats every result to avoid showing it.

Does this work for area or volume?

No — this converts one-dimensional lengths only (metres, feet, miles and so on). Converting an area (m²) or volume (m³) needs the factor squared or cubed, which is a different calculation.

A length converter that avoids the usual rounding mess

Every conversion here routes through metres as a single base unit rather than a direct factor for every possible pair. That matters more than it sounds: a converter with a separate constant for each pair of units — inches to yards, yards to nautical miles, and so on — has as many places to get a constant slightly wrong as it has pairs. Routing through one base unit means there is exactly one factor to trust per unit, and the result never drifts depending on which two units you happen to pick.

Millimetres, centimetres, metres and kilometres cover the metric side. Inches, feet, yards and miles cover imperial. The nautical mile — defined as exactly 1,852 metres internationally — is included separately, since it turns up in aviation, shipping and GPS coordinates and is easy to confuse with the older, slightly different Admiralty mile.

When you'd use this

Converting a recipe or a woodworking measurement between metric and imperial. Checking a shipping dimension given in inches against a metric spec sheet. Working out a flight or sailing distance in nautical miles against a road distance in kilometres. Anywhere a quick, exact conversion beats doing the arithmetic by hand.

Limitations

This converts length only — one dimension. Area (square metres, acres) and volume (litres, cubic feet) use different factors entirely and are not covered here.