Unit Conversion Calculator

Convert units instantly: Change any value and see all equivalent results at once.

Instructions

This is a fast unit converter based on the International System of Units (SI), the modern form of the metric system and the world's most widely used system of measurement. Each unit is linked to its SI definition; it converts by storing the SI value internally and deriving the rest from it.

Type a number in any box. All other boxes update instantly. Use the arrow keys for fine adjustments. Values are calculated directly against SI units for accuracy.

Units used in this tool

Formulas are expressed relative to the SI base unit.

Legend:

For linear units (length, area, volume, mass, time, speed, pressure):
SI = Unit × factor and Unit = SI ÷ factor

For temperature we list both directions explicitly.

Length (SI base: meter, m)

• Micrometer (µm): m = µm × 1e-6
• Millimeter (mm): m = mm × 1e-3
• Centimeter (cm): m = cm × 1e-2
• Inch (in): m = in × 0.0254 (exact)
• Foot (ft): m = ft × 0.3048 (exact)
• Yard (yd): m = yd × 0.9144 (exact)
• Meter (m): m = m × 1
• Kilometer (km): m = km × 1000
• Mile (mi): m = mi × 1609.344 (exact)
• Nautical mile (nmi): m = nmi × 1852 (exact)

Area (SI base: square meter, m²)

• Square millimeter (mm²): m² = mm² × 1e-6
• Square centimeter (cm²): m² = cm² × 1e-4
• Square inch (in²): m² = in² × 0.00064516 (exact)
• Square foot (ft²): m² = ft² × 0.09290304 (exact)
• Square yard (yd²): m² = yd² × 0.83612736 (exact)
• Square meter (m²): m² = m² × 1
• Are (a): m² = a × 100
• Acre (ac): m² = ac × 4046.8564224 (international acre; exact)
• Hectare (ha): m² = ha × 10000
• Square kilometer (km²): m² = km² × 1e6

Volume (SI base: cubic meter, m³)

• Microliter (µL): m³ = µL × 1e-9
• Milliliter (mL): m³ = mL × 1e-6
• Centiliter (cL): m³ = cL × 1e-5
• Deciliter (dL): m³ = dL × 1e-4
• Liter (L): m³ = L × 1e-3
• Cubic centimeter (cm³): m³ = cm³ × 1e-6
• Cubic inch (in³): m³ = in³ × 0.000016387064 (exact)
• Cubic foot (ft³): m³ = ft³ × 0.028316846592 (exact)
• Gallon (US): m³ = gal × 0.003785411784 (US liquid; exact)
• Cubic meter (m³): m³ = m³ × 1

Mass (SI base: kilogram, kg)

• Microgram (µg): kg = µg × 1e-9
• Milligram (mg): kg = mg × 1e-6
• Carat (ct): kg = ct × 0.0002 (exact)
• Gram (g): kg = g × 1e-3
• Ounce (av) (oz): kg = oz × 0.028349523125 (avoirdupois; exact)
• Pound (av) (lb): kg = lb × 0.45359237 (exact)
• Kilogram (kg): kg = kg × 1
• Stone (st): kg = st × 6.35029318 (exact)
• US short ton (US ton): kg = ton × 907.18474 (exact)
• Metric tonne (t): kg = t × 1000

Time (SI base: second, s)

• Nanosecond (ns): s = ns × 1e-9
• Microsecond (µs): s = µs × 1e-6
• Millisecond (ms): s = ms × 1e-3
• Second (s): s = s × 1
• Minute (min): s = min × 60
• Hour (h): s = h × 3600
• Day (day): s = day × 86400
• Week (week): s = week × 604800
• Month (30d): s = month × 2592000 (fixed 30-day month, by design)
• Year (365d): s = year × 31536000 (fixed 365-day year, by design)

Speed (SI base: meter per second, m/s)

• Millimeter per second (mm/s): m/s = mm/s × 0.001
• Centimeter per second (cm/s): m/s = cm/s × 0.01
• Meter per minute (m/min): m/s = m/min × 1/60
• Inch per second (in/s): m/s = in/s × 0.0254 (exact)
• Kilometer per hour (km/h): m/s = km/h × 1000/3600 (= 0.277… exact)
• Foot per second (ft/s): m/s = ft/s × 0.3048 (exact)
• Mile per hour (mph): m/s = mph × 1609.344/3600 (= 0.44704 exact)
• Knot (kn): m/s = kn × 1852/3600 (= 0.514444… exact)
• Meter per second (m/s): m/s = m/s × 1
• Kilometer per minute (km/min): m/s = km/min × 1000/60

Pressure (SI base: pascal, Pa)

• Pascal (Pa): Pa = Pa × 1
• Centimeter of water (cmH₂O): Pa = cmH₂O × 98.0665 (by convention, 4 °C)
• Millimeter of mercury (mmHg): Pa = mmHg × 133.322387415 (conventional, 0 °C)
• Kilopascal (kPa): Pa = kPa × 1000
• Inch of mercury (inHg): Pa = inHg × 3386.388640341 (conventional, 0 °C)
• Pound per square inch (psi): Pa = psi × 6894.757293168361
• Meter of water (mH₂O): Pa = mH₂O × 9806.65
• Bar (bar): Pa = bar × 100000 (exact)
• Standard atmosphere (atm): Pa = atm × 101325 (exact)
• Megapascal (MPa): Pa = MPa × 1e6

Temperature (SI base: kelvin, K)

• Kelvin (K): K = K; K → °C: °C = K − 273.15
• Celsius (°C): K = °C + 273.15; °C = K − 273.15
• Fahrenheit (°F): K = (°F − 32) × 5/9 + 273.15; °F = (K − 273.15) × 9/5 + 32
• Rankine (°R): K = °R × 5/9; °R = K × 9/5
• Delisle (°De): K = 373.15 − (°De × 2/3); °De = (373.15 − K) × 3/2
• Réaumur (°Re): K = 273.15 + °Re/0.8; °Re = (K − 273.15) × 0.8
• Rømer (°Rø): K = 273.15 + (°Rø − 7.5) × 40/21; °Rø = (K − 273.15) × 21/40 + 7.5
• Newton (°N): K = 273.15 + °N × 100/33; °N = (K − 273.15) × 33/100

Notes: Liter is accepted for use with SI (1 L = 1e-3 m³). "Acre" here uses the international acre (4046.8564224 m²). Pressure units like mmHg/inHg use the conventional definitions shown above.

About the long decimals

You may see values like 0.9999999996. That's normal floating-point behavior: many decimals cannot be represented exactly in binary. We keep full precision to handle very large and very small numbers; long successions of the same decimal, specially near-integers like 0.9999… or 1.0000…1 (most likely means 1) should be interpreted with this in mind.