Length Converter

A live length and distance converter that turns any measurement into 16 different units at once — from nanometres up to light-years. Unlike a basic two-field tool, every row in the grid is editable: type into millimetres, feet, or nautical miles and the whole grid re-fills instantly so you can read the same length in every unit side by side. It is built for engineers, students, makers, sailors, runners and anyone who routinely jumps between metric and imperial.

How it works

Internally the tool keeps a single source of truth: your length stored in metres, the SI base unit. Each unit is defined by exactly how many metres one of it equals — for example a foot is exactly 0.3048 m and a mile is exactly 1609.344 m. When you type a value, the tool multiplies it by that unit’s metre-factor to get the canonical length, then divides by every other unit’s factor to fill the grid. Because all conversions route through one base unit, the metric/imperial factors are the internationally agreed exact definitions rather than rounded approximations, and there is no drift from chaining conversions.

The headline From/To pair gives you a clean single answer plus the exact one-unit factor (for instance “1 m equals 3.2808399 ft”), and the swap button flips the direction in place. Values are formatted to up to 8 significant figures with trailing zeros trimmed, and very small or very large results (like light-years) fall back to scientific notation so the display stays readable.

Worked example

Suppose you have a worktop that is 2.4 metres long and you need it in feet and inches. Type 2.4 into the metres row. The grid immediately shows 7.8740157 ft, 94.488189 in and 2.6246719 yd. Set the From unit to metres and the To unit to feet and the headline reads 2.4 m = 7.8740157 ft. If instead you are planning a 5 kilometre run and want it in miles, the grid shows 3.1068560 miles — just over a 5K’s familiar 3.1-mile figure.

Conversion reference table

Every figure above is reproduced live by the grid when you enter a value of 1 in the matching unit. All of it runs locally in your browser — no numbers are uploaded or stored.