Math

Unit Converter

Convert common length units through SI metres. Uses exact factors such as 1 inch = 2.54 cm and 1 international foot = 0.3048 m.

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The formula

Convert the source value to metres, then divide by the target unit’s metre factor. Factors are exact international definitions.

target = value × (metres_per_from ÷ metres_per_to)

Worked example

  1. 100 cm → metres
  2. 100 × 0.01 m/cm = 1 m
  3. 1 m → feet: 1 ÷ 0.3048 ≈ 3.28084 ft

Result: 100 cm = 1 m ≈ 3.28084 ft

How length conversion works

Every length unit here is a fixed multiple of the metre. Converting A → B is multiplying by the ratio of those multiples.

Factors used

cm = 0.01 m, m = 1, km = 1000 m, inch = 0.0254 m (exact), foot = 0.3048 m (exact international foot), mile = 1609.344 m (exact for the international mile).

Survey foot note

Older U.S. survey definitions can differ by tiny amounts in GIS and land records. Everyday conversion uses the international foot above.

What we do not model

No area, volume, mass, or nautical miles. For room area, use the area calculator after converting side lengths if needed.

Interesting facts

Metric system

All but three countries (US, Liberia, Myanmar) officially use the metric system for most measurements.

SI prefixes

Kilo-, centi-, and milli- are powers of ten. That decimal structure is why metric conversions are often mental arithmetic.

Exact vs survey feet

Since 1959 the international foot is exactly 0.3048 m. Older US survey definitions can differ by tiny amounts in GIS work.

Imperial still in niches

Even metric countries keep miles on roads, pints in pubs, or inches on screens — customary units linger in culture.

Dimensional check

Writing units through a calculation catches errors: you cannot add meters to seconds without a conversion factor that makes sense.

Frequently asked questions

Multiply inches by 2.54 (exact). Example: 10 in × 2.54 = 25.4 cm. Select in → cm in the converter.

They use standard exact factors (1 in = 0.0254 m exactly; 1 ft = 0.3048 m exactly). Display rounding may shorten trailing digits.

1 ÷ 0.3048 ≈ 3.28084 feet per metre.

Yes for the international mile used here. Nautical miles are different and not included.

This tool is length-only. Use the area calculator for m²/ft² from length × width.

References

  1. SI units — National Institute of Standards and Technology (NIST) Official U.S. metrology guidance for SI units.
  2. NIST SP 811 — Guide to the SI — National Institute of Standards and Technology Conversion factors and proper unit notation.
  3. BIPM SI Brochure — Bureau International des Poids et Mesures International definitions of the metre and related units.