Chemistry Unit Converter
Convert between temperature, pressure, mass, volume, energy, and amount of substance with step-by-step explanations.
Need a refresher on units? Read the Numbers, Units & Measurement study guide →
How It Works
Most unit conversions use a simple two-step process: convert the input to a standard base unit, then convert from the base unit to the target. For example, pressure conversions go through atmospheres (atm) as the base.
Temperature is the exception: Celsius, Fahrenheit, and Kelvin are related by non-linear formulas. °F = °C × 9/5 + 32, and K = °C + 273.15. These are shown in the conversion steps so you can follow the math.
This tool covers the unit categories most common in general chemistry: temperature for thermodynamics, pressure for gas laws, mass and volume for stoichiometry and solutions, energy for enthalpy and bond energies, and amount of substance for mole conversions.
Definitions and constants follow the NIST SI guidance and current SI defining constants. Most listed conversion factors are exact definitions; the atomic mass unit conversion carries measurement uncertainty.
Frequently Asked Questions
How do you convert Celsius to Kelvin?
Add 273.15 to the Celsius temperature: K = °C + 273.15. To convert back, subtract 273.15. The Kelvin scale starts at absolute zero, so it has no negative values.
How do you convert between atm, Pa, and mmHg?
Standard atmospheric pressure is 1 atm = 101,325 Pa = 760 mmHg (torr) = 1.01325 bar. Convert by multiplying or dividing by these equivalences.
How do you convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 and add 32: °F = (°C × 9/5) + 32. To reverse it, subtract 32 first, then multiply by 5/9.
What units does this converter support?
Temperature (K, °C, °F), pressure (atm, Pa, mmHg, bar), mass, volume, energy, and amount of substance (moles), with the conversion steps shown for each.
Why does chemistry use Kelvin instead of Celsius?
Kelvin is an absolute temperature scale whose zero is absolute zero. Gas-law and thermodynamic equations require absolute temperature, so values must be converted to Kelvin for calculations such as PV = nRT.