Unit Conversion

Length Converter

Convert between millimetres, centimetres, metres, kilometres, inches, feet, yards and miles.

Formula and sources updated · 2026-10-04Data sources · 1View algorithm, constants and default inputs (JSON)

Example

Decimal places

1 ft = 0.3048 m

About this calculator

Length conversions use fixed international definitions rather than approximations: an inch has been exactly 25.4 millimetres since 1959, and every other imperial unit follows from it.

Worked example

calculated with the default values below

Value 1 · From Metres (m) · To Feet (ft) · Decimal places 4 Result 3.2808 · In metres 1.000000 m · In feet 3.280840 ft

Method and assumptions

Formula basis and scope

Convert lengths via metres using the selected international-unit factors.

Only the displayed unit definitions are converted; rounding and measurement uncertainty are separate.

Data sources

NIST SP 811 — Conversion factors by quantity

Disclaimer

These calculators give general conversion results. Rounding and the precision of the value you enter both affect the output, so treat displayed decimals as indicative rather than exact.

Maintained by: CalcDelta Formula and sources updated · 2026-10-04

Implementation source

This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.

View algorithm, constants and default inputs (JSON)

Formula and variables

result = value × F[from] ÷ F[to]; F: mm → 0.001, cm → 0.01, m → 1, km → 1000, in → 0.0254, ft → 0.3048, yd → 0.9144, mi → 1609.344

value: length amount
from: source unit
to: target unit
F: metres per unit (lookup table)
result: converted length

All values are converted through metres; feet value = metres ÷ 0.3048.

Embed this calculator

Copy the iframe snippet to place this calculator on your site. No account required. The snippet stays in sync with the inputs currently shown.

<iframe src="https://calcdelta.com/length-calculator/" title="Length Converter" loading="lazy" referrerpolicy="no-referrer-when-downgrade" style="width:100%;max-width:480px;height:720px;border:0;border-radius:12px;"></iframe>

Frequently asked questions

Why is the metre to feet conversion an exact definition?

Since 1959 the inch has been defined as exactly 25.4 millimetres, so every conversion in this tool is a fixed factor, not a rounded approximation. One metre therefore equals 3.28084 feet every time, and a foot is exactly 0.3048 metres. Because the factors are exact, converting 1 metre to feet and back returns the original value with no drift.