What is Length Converter?

Length Converter converts between metric and imperial units. Go from nanometers to inches, kilometers to miles, or any of 11 common length units (including nautical miles) with results precise to 10 significant digits.

Conversions chain through meters internally, so the math is consistent across all 11 units (nm, µm, mm, cm, m, km, in, ft, yd, mi, nmi). A decimals control lets you round the result to 2, 4, 6 or 8 places or keep full precision, the visual ruler underneath shows where the values fall relative to each other, an all-units panel mirrors the same value across every unit at once, quick presets jump straight to the most common pairings, and a swap button flips From and To without retyping the number.

How to use

1. Enter a numeric value in the input field and select the source unit (e.g., centimeters).
2. Select the target unit you want to convert to (e.g., inches).
3. The converted value appears instantly. Use the swap button to quickly reverse the conversion direction.

When to use

• Checking if a 60-inch TV fits a 1.4 m wide media console before buying.
• Reading a recipe or pattern that mixes centimetres and inches.
• Translating a marathon route described in kilometres into miles for a US running app.

Result

A furniture buyer sees a desk listed as 120 cm wide and needs to know if it fits a 48-inch space. They enter 120, switch from 'cm' to 'inches', and get 47.24 inches. It fits, with room to spare.

FAQ

How many decimal places does the result keep?

Your choice. The Decimals buttons round the result to 2, 4, 6 or 8 places, or pick Full for up to 10 significant digits — fine for engineering work down to micrometre scale. Very small or very large numbers switch to scientific notation so the precision isn't lost in trailing zeros or rounding.

Are the conversion factors exact or rounded?

Imperial-to-metric values use the internationally defined exact factors: 1 inch is exactly 25.4 mm, 1 mile is exactly 1609.344 m. There's no rounding inside the conversion itself; rounding only happens at display time.

Why does 1 foot give 30.48 cm but a measuring tape sometimes reads 30.5 cm?

Tapes and rulers often round to the nearest visible tick. The mathematical value is 30.48 cm exactly; physical tapes split a centimetre into 10 marks and 0.48 cm sits between two of them, so the eye reads the closer 30.5 mark.

Can I convert nautical miles or astronomical units?

Nautical miles are now a first-class unit in the dropdowns (1 nmi = 1852 m exactly), so maritime, aviation and geography conversions work without manual math. Astronomical units aren't included yet — for AU treat any back-of-envelope answer as approximate due to scale.

Why does the result swap when I click the arrows?

The swap button reverses the From and To units while keeping the original number. So if you were converting 100 cm to inches, one click shows what 100 inches is in centimetres instead, useful for spot-checking the inverse direction.

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