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Length Converter

Convert between metres, kilometres, miles, feet, inches, yards, nautical miles and over 130 historical and regional units grouped by region.

Enter the values to see the result here.

Formula

Every unit is stored as a multiple of the metre. A conversion goes through the metre:

xto=xfrom×ffromftox_{\text{to}} = x_{\text{from}} \times \frac{f_{\text{from}}}{f_{\text{to}}}

where ff is the number of metres in one unit: kilometre 1000, mile 1609.344, yard 0.9144, foot 0.3048, inch 0.0254, nautical mile 1852.

Worked example

Convert 5 miles to kilometres.

  • fmi=1609.344f_{\text{mi}} = 1609.344 m and fkm=1000f_{\text{km}} = 1000 m.
  • 5×1609.344/1000=8.046725 \times 1609.344 / 1000 = 8.04672 km.

A shortcut, 1 mile ≈ 1.6 km, gives 8 km, an error of 0.6%. For long distances use the exact factor: over a 26.2-mile marathon the shortcut is off by about 0.25 km.

Common mistakes

  • Using 1 mile = 1.6 km for exact work.
  • Confusing the nautical mile with the statute mile.
  • Converting a height of 5 ft 9 in as 5.9 ft. Nine inches is 0.75 ft, so it is 5.75 ft.
  • Typing a comma as a decimal separator in one field and a point in another. Either works here, but be consistent.

Frequently asked questions

How many centimetres are in a foot?

Exactly 30.48. Since 1959 the international yard has been defined as 0.9144 metres, so a foot (a third of a yard) is 0.3048 m and an inch is 2.54 cm, with no rounding.

Is the nautical mile the same as the ordinary mile?

No. A nautical mile is 1,852 m, about 1.15 statute miles. It was defined from one minute of latitude, which is why ships and aircraft use it with knots.

How do I convert height like 5 ft 9 in?

Convert feet to inches (5 × 12 = 60), add the inches (69), then convert 69 in to centimetres: 175.26 cm.

Why does the table show so many digits?

The table gives your value in every unit at once. Values below 1 keep six significant digits (so 5 mm in kilometres reads 0.000005), and extremely large or small values switch to scientific notation.

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