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Length Converter

Convert mm, cm, metres, kilometres, inches, feet, yards, miles and nautical miles.

By CalcHub Editorial · Last reviewed

Quick answer

  • Formula: Result = Value × (factor of from-unit in metres) ÷ (factor of to-unit in metres)
  • Worked example — Converted length: 3.106856 (full example below).

Length Converter

Worked example result
Converted length3.106856
Summary5 km = 3.106856 mi

5 kilometres is 3.106856 miles — most runners round a 5K to about 3.1 miles.

Diagram: how the Length Converter works — you enter Length, From, To; it applies the formula Result = Value × (factor of from-unit in metres) ÷ (factor of to-un…; and the worked example gives Converted length: 3.106856.
How the Length Converter works — the inputs, the formula, and a worked example (Converted length: 3.106856).

Convert between metric and imperial lengths through the metre, using the exact definitions from the 1959 international yard and pound agreement: 1 inch = 25.4 mm exactly, 1 foot = 0.3048 m, 1 yard = 0.9144 m and 1 mile = 1609.344 m. A nautical mile is exactly 1852 m.

Because every factor is exact, conversions here are precise — 1 inch is exactly 2.54 cm, not an approximation.

The formula

Result = Value × (factor of from-unit in metres) ÷ (factor of to-unit in metres)

Worked example

5 kilometres is 3.106856 miles — most runners round a 5K to about 3.1 miles.

Worked example for the Length Converter: with Length 5, From Kilometres (km), To Miles (mi), the result is Converted length: 3.106856; Summary: 5 km = 3.106856 mi.
The worked example, with the example values entered and the results they give.

The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.

Frequently asked questions

How many centimetres are in an inch?

Exactly 2.54 cm. The inch has been defined as exactly 25.4 mm since 1959, so this conversion has no rounding error.

What is a nautical mile used for?

Navigation at sea and in the air. One nautical mile is exactly 1852 m and equals one minute of arc of latitude; speeds in nautical miles per hour are called knots.

How do I convert miles to kilometres quickly?

Multiply by 1.609344. For a rough mental estimate, multiply by 1.6 or use the Fibonacci trick (5 miles ≈ 8 km).

Category: Unit Conversions calculators

Sources & methodology

This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.

Content last reviewed by CalcHub Editorial.

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