Online chemistry calculator

This chemistry calculator handles the everyday calculations of the chemistry classroom and lab: converting between mass and moles, working out molarity (concentration), applying the ideal gas law, and calculating percent yield. Choose a calculation, enter your values, and get the answer with the correct units.

Moles, mass and molarity

The mole is the chemist’s counting unit. The number of moles equals mass divided by molar mass (n = m ÷ M), so you will often need the molar mass first — find it with our molecular weight calculator. Molarity (C = n ÷ V) gives the concentration of a solution in moles per litre, and is the basis for preparing and diluting solutions.

The ideal gas law

The ideal gas law, PV = nRT, links pressure, volume, amount, and temperature of a gas. This calculator uses R = 0.082057 L·atm·mol⁻¹·K⁻¹, so enter pressure in atmospheres, volume in litres, and temperature in kelvin. To convert temperatures, use our temperature converter, and for solution prep see the dilution calculator.

Frequently asked questions

What units does the ideal gas law need?

With R = 0.082057, use atmospheres for pressure, litres for volume, moles for amount, and kelvin for temperature. Always convert °C to K by adding 273.15.