Unit Converter for Chemistry & Physics
Pick a quantity, type a value and see it in every unit at once. Exact SI factors, including the post-2019 definitions of the mole and the kelvin.
Quantity
| Unit | Value |
|---|---|
| Pa pascal | 101,325 |
| kPa kilopascal | 101.325 |
| atm atmosphere | 1 |
| bar bar | 1.01325 |
| mbar millibar | 1,013.25 |
| mmHg millimetre of mercury | 759.9999 |
| torr torr | 760 |
| psi pound per square inch | 14.69595 |
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Conversions students ask about most
- mL to L: divide by 1000. 250 mL = 0.250 L. Needed for every molarity calculation.
- °C to K: add 273.15. Gas laws always need kelvin.
- km/h to m/s: divide by 3.6. 100 km/h = 27.8 m/s.
- kPa to atm: divide by 101.325.
- kWh to J: multiply by 3.6 × 10⁶.
- g/cm³ to kg/m³: multiply by 1000.
Frequently asked questions
Which units does this converter cover?
Length, mass, time, speed, acceleration, force, energy, power, pressure, volume, temperature, amount of substance, concentration, density, momentum, angle, area and molar mass: the quantities that come up in general chemistry and introductory physics.
How accurate are the conversion factors?
Exact where the definition is exact (1 in = 2.54 cm, 1 atm = 101 325 Pa, 1 cal = 4.184 J, Avogadro constant = 6.02214076 × 10²³ mol⁻¹ since the 2019 SI redefinition), otherwise to at least 10 significant figures from NIST Special Publication 811.
How do I convert Celsius to kelvin?
Add 273.15: K = °C + 273.15. Fahrenheit to Celsius is °C = (°F − 32) × 5/9. Temperature conversions have an offset, so they are not simple multiplications like other units.
How do I convert mmHg or torr to atm?
1 atm = 760 torr ≈ 760 mmHg (they differ in the 7th significant figure). Divide by 760. 1 atm is also 101.325 kPa and 1.01325 bar.
What is dimensional analysis?
Multiplying by conversion factors written as fractions equal to 1 (e.g. 1000 mL / 1 L) so the unwanted units cancel. It is the same idea this converter uses: convert to the SI unit, then to the target.