Unit Conversion Formulas

Every unit conversion uses a formula to translate a value from one unit to another. Most conversions involve multiplying or dividing by a fixed factor. Temperature is the exception, requiring offset formulas because the scales have different zero points. Browse the formulas below for step-by-step worked examples.

Common Conversion Formulas

km × 0.621371 = mi

kg × 2.204623 = lb

°F = °C × 9/5 + 32

mph × 1.609344 = km/h

L × 0.264172 = gal

MB ÷ 1,000 = GB

Jump to: Length / Distance Weight / Mass Speed Volume / Capacity Data / Storage Temperature

straightenLength / Distance Formulas

Length conversions use fixed ratios based on metric definitions (meters, kilometers) and imperial equivalents (miles, feet, inches).

functions Kilometer to Milekm × 0.621371 = mi functions How to convert km to mkm × 1,000 = m functions km to ft equationkm × 3,280.8399 = ft functions Kilometer to Inchkm × 39,370.0787 = in functions How to convert km to cmkm × 100,000 = cm functions km to mm equationkm × 1,000,000 = mm functions Kilometer to Yardkm × 1,093.6133 = yd functions How to convert mi to kmmi × 1.609344 = km functions mi to m equationmi × 1,609.344 = m functions Mile to Footmi × 5,280 = ft functions How to convert mi to inmi × 63,360 = in functions mi to cm equationmi × 160,934.4 = cm

Try: 5 km to miles 12 inches to cm

scaleWeight / Mass Formulas

Weight conversions relate metric units (kilograms, grams) to imperial units (pounds, ounces, stone) using internationally standardized factors.

functions Kilogram to Poundkg × 2.204623 = lb functions How to convert kg to gkg × 1,000 = g functions kg to oz equationkg × 35.273962 = oz functions Kilogram to Milligramkg × 1,000,000 = mg functions How to convert kg to stkg × 0.157473 = st functions kg to t equationkg ÷ 1,000 = t functions Pound to Kilogramlb × 0.453592 = kg functions How to convert lb to glb × 453.59237 = g functions lb to oz equationlb × 16 = oz functions Pound to Milligramlb × 453,592.37 = mg functions How to convert lb to stlb ÷ 14 = st functions lb to t equationlb × 0.00045359 = t

Try: 70 kg to lb 100 grams to oz

speedSpeed Formulas

Speed conversions translate between road speed units (mph, km/h), scientific units (m/s), and nautical units (knots).

functions Mile per Hour to Kilometer per Hourmph × 1.609344 = km/h functions How to convert mph to m/smph × 0.44704 = m/s functions mph to kn equationmph × 0.868977 = kn functions Mile per Hour to Foot per Secondmph × 1.466667 = ft/s functions How to convert km/h to mphkm/h × 0.621371 = mph functions km/h to m/s equationkm/h ÷ 3.6 = m/s functions Kilometer per Hour to Knotkm/h × 0.539957 = kn functions How to convert km/h to ft/skm/h × 0.911344 = ft/s functions m/s to mph equationm/s × 2.236936 = mph functions Meter per Second to Kilometer per Hourm/s × 3.6 = km/h functions How to convert m/s to knm/s × 1.943846 = kn functions m/s to ft/s equationm/s ÷ 0.3048 = ft/s

Try: 60 mph to km/h 10 knots to mph

water_dropVolume / Capacity Formulas

Volume conversions bridge metric units (liters, milliliters) and US customary units (gallons, cups, fluid ounces, tablespoons).

functions Liter to GallonL × 0.264172 = gal functions How to convert L to mLL × 1,000 = mL functions L to cup equationL × 4.226753 = cup functions Liter to Fluid OunceL × 33.814023 = fl oz functions How to convert L to ptL × 2.113376 = pt functions L to qt equationL × 1.056688 = qt functions Liter to TablespoonL × 67.628045 = tbsp functions How to convert L to tspL × 202.884136 = tsp functions gal to L equationgal × 3.785412 = L functions Gallon to Millilitergal × 3,785.4118 = mL functions How to convert gal to cupgal × 16 = cup functions gal to fl oz equationgal × 128 = fl oz

Try: 10 liters to gallons 2 cups to ml

storageData / Storage Formulas

Data conversions scale between storage units (KB, MB, GB, TB) and translate between bits and bytes for understanding transfer speeds.

functions Byte to KilobyteB ÷ 1,000 = KB functions How to convert B to MBB ÷ 1,000,000 = MB functions B to GB equationB ÷ 1,000,000,000 = GB functions Byte to TerabyteB ÷ 1,000,000,000,000 = TB functions How to convert B to PBB ÷ 1,000,000,000,000,000 = PB functions B to Mb equationB ÷ 125,000 = Mb functions Byte to GigabitB ÷ 125,000,000 = Gb functions How to convert KB to BKB × 1,000 = B functions KB to MB equationKB ÷ 1,000 = MB functions Kilobyte to GigabyteKB ÷ 1,000,000 = GB functions How to convert KB to TBKB ÷ 1,000,000,000 = TB functions KB to PB equationKB ÷ 1,000,000,000,000 = PB

Try: 500 MB to GB 1000 GB to TB

thermostatTemperature Formulas

Temperature conversions use offset formulas rather than simple multiplication, because Celsius, Fahrenheit, and Kelvin have different zero points.

functions Celsius to Fahrenheit°F = °C × 9/5 + 32 functions How to convert °C to KK = °C + 273.15 functions °F to °C equation°C = (°F - 32) × 5/9 functions Fahrenheit to KelvinK = (°F - 32) × 5/9 + 273.15 functions How to convert K to °C°C = K - 273.15 functions K to °F equation°F = (K - 273.15) × 9/5 + 32

Try: 100 °C to °F 72 °F to °C

Frequently Asked Questions

What is a unit conversion formula? expand_more

A unit conversion formula is a mathematical equation that converts a value from one unit to another. Most formulas involve multiplying or dividing by a fixed conversion factor. Temperature conversions are an exception, requiring offset formulas because the scales have different zero points.

Are conversion factors exact or approximate? expand_more

Some conversion factors are exact by international definition (e.g., 1 inch = exactly 2.54 cm, 1 foot = exactly 0.3048 m). Others are derived from exact definitions but produce long decimals when inverted. All formulas on UnitCompare use standard factors defined by international agreements.

Why are some results rounded? expand_more

Displayed results are rounded for readability. The calculators use full-precision factors internally. Each formula page shows the exact factor used in the conversion.

How do I convert units without a calculator? expand_more

Use the conversion formula for the unit pair and do the arithmetic by hand. Many common conversions have mental math shortcuts (e.g., multiply km by 0.6 for miles, double Celsius and add 30 for Fahrenheit). Each converter page includes a Quick Mental Conversion section where available.