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Unit Converter — Metric & Imperial

Convert between metric and US/UK customary units across six categories. Check the conversion factor or formula beside the result.

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Result—
1 m = 3.2808399 ft

Conversion factors follow widely used standards (NIST SP 811). Temperature conversions are exact identities.

Popular conversions

Single-purpose pages for the conversions people look up most, each with a full chart and the formula.

Centimetres to Inches ×0.394 Inches to Centimetres ×2.54 Millimetres to Inches ×0.039 Inches to Millimetres ×25.4 Metres to Feet ×3.281 Feet to Metres ×0.305 Kilometres to Miles ×0.621 Miles to Kilometres ×1.609 Kilograms to Pounds ×2.205 Pounds to Kilograms ×0.454 Grams to Ounces ×0.035 Ounces to Grams ×28.35 Celsius to Fahrenheit Fahrenheit to Celsius Celsius to Kelvin Kelvin to Celsius Litres to US gallons ×0.264 US gallons to Litres ×3.785 Millilitres to US fluid ounces ×0.034 US fluid ounces to Millilitres ×29.574 Kilometres per hour to Miles per hour ×0.621 Miles per hour to Kilometres per hour ×1.609 Knots to Miles per hour ×1.151 Square metres to Square feet ×10.764 Square feet to Square metres ×0.093 Acres to Hectares ×0.405 Hectares to Acres ×2.471

How to use

  1. Pick a category — length, mass, volume, area, speed or temperature. Sensible default units load automatically.
  2. Enter a value and choose the unit you are converting from.
  3. Choose the target unit. The result updates instantly — there is no convert button.
  4. Use the swap button to flip the direction without re-picking both units.

Questions

Which conversion factors do you use?

The internationally agreed values published by NIST (SP 811) — for example exactly 0.3048 m per foot and 0.45359237 kg per pound. Temperature uses the exact defining formulas rather than approximations.

Why are US and UK gallons different?

They use different definitions. A US liquid gallon is 3.785411784 L; an imperial gallon is 4.54609 L — about 20% larger. Both are listed separately so recipes and fuel figures do not get mixed up.

Why does the result show only six decimals?

Display is capped at six fractional digits for readability. The calculation itself runs at full double precision.

Examples and checks

Select the physical quantity before the units. A mass ounce and a fluid ounce share a name but measure different things; converting between them requires the substance’s density.

Convert a length

Input or situation
254 centimetres to inches
Result
100 inches

One inch is exactly 2.54 centimetres, so 254 ÷ 2.54 = 100.

Convert a temperature

Input or situation
20 °C to °F
Result
68 °F

Use 20 × 9 ÷ 5 + 32. Temperature scales have different zero points, so multiplying by a factor alone is insufficient.

Before you use the result

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Guides for this task

Guide Ounces vs fluid ounces: weight and volume explained Understand the difference between oz and fl oz, choose US or imperial fluid ounces, and use ingredient density when converting between mass and volume. Guide US, metric and imperial cups: measurement differences Compare US customary, metric and imperial cup sizes. Choose the right measure for a recipe and understand when the difference affects ingredients. Guide Cups to grams: why the ingredient matters A cup measures volume and grams measure mass. See why flour, sugar and honey need different conversions, and how to choose the right cup size.

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