Unit converter
Convert length, area, volume, mass, temperature, speed, time, pressure and energy between metric and US/imperial units.
Your inputs stay in your browser. Displayed results are rounded to a maximum of 12 significant digits.
Method and assumptions
Method version 1.2.0 · Updated
Length
Formula: y = x × f(from) ÷ f(to)
Lengths must be zero or positive. Inches, feet, yards and miles use international definitions.
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Mass
Formula: y = x × f(from) ÷ f(to)
Masses must be zero or positive. Pounds and ounces are avoirdupois units, not troy units.
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Temperature
Formula: °F = °C × 9/5 + 32 ; °C = (°F − 32) × 5/9 ; K = °C + 273.15
Negative temperatures are accepted in Celsius and Fahrenheit, down to absolute zero.
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Area
Formula: y = x × f(from) ÷ f(to)
Areas must be zero or positive. Square feet, inches and yards use international definitions. Example: 1 ha = 10,000 m².
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Volume
Formula: y = x × f(from) ÷ f(to)
Volumes must be zero or positive. US liquid gallons and fluid ounces differ from imperial units; dry gallons are excluded. Example: 1 US liquid gallon = 3.785411784 L.
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Speed
Formula: y = x × f(from) ÷ f(to)
Non-negative values: speed magnitude only, without direction. A knot is one international nautical mile per hour. Example: 36 km/h = 10 m/s.
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Time
Formula: y = x × f(from) ÷ f(to)
Non-negative fixed durations: 1 day = 24 h and 1 week = 7 days. No calendar arithmetic, months, years or daylight-saving changes. Example: 1.5 h = 90 min.
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Pressure
Formula: y = x × f(from) ÷ f(to)
Non-negative pressures. Unit conversion only: keep the same reference, absolute or gauge. Atmospheric pressure is not added. Example: 1 bar = 100 kPa.
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Energy
Formula: y = x × f(from) ÷ f(to)
Non-negative energy, without power or cost calculations. Calories use the thermochemical definition: 1 cal = 4.184 J. Example: 1 kWh = 3,600,000 J.
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Deterministic floating-point calculation. The displayed result is rounded to a maximum of 12 significant digits.
Sources: NIST — SI conversion factors.