Molarity calculator
Relate concentration, volume and moles. Leave the unknown blank.
Work it out
Fill in all but one. 3 boxes are empty, so there is more than one answer.
A worked example
You need 250 mL of 0.1 M sodium chloride.
0.025 mol, which is 1.46 g of NaCl
- 1n = c × V = 0.1 mol/L × 0.250 L = 0.025 mol.
- 2NaCl has a molar mass of 58.44 g/mol.
- 3m = n × M = 0.025 × 58.44 = 1.46 g. Dissolve that and make up to 250 mL.
What this assumes
- Volume is the final volume of the solution. Adding solute to a measured volume of solvent gives a slightly different answer from making up to the mark.
- Molarity changes with temperature because the solution's volume does. Molality (mol per kg of solvent) does not, which is why it is preferred for work over a temperature range.
The terms used here
- Molarity
- Moles of solute per litre of solution, written M.
- Mole
- 6.022 × 10²³ particles — the bridge between a mass you can weigh and a number of molecules.
- Making up to volume
- Dissolving the solid in less solvent, then adding solvent until the total reaches the mark.
The other calculators
Molar mass calculator
Enter a formula and get its molar mass, broken down by element.
Dilution calculator (C₁V₁ = C₂V₂)
C₁V₁ = C₂V₂. Leave the unknown blank.
Percent yield calculator
Actual over theoretical, as a percentage. Leave the unknown blank.
Beer–Lambert law calculator
A = εlc. Leave the unknown blank.
pH, pOH and [H⁺] calculator
Convert between pH, pOH, [H⁺] and [OH⁻]. Leave the unknown blank.
Buffer pH calculator (Henderson–Hasselbalch)
pH = pKa + log([A⁻]/[HA]). Leave the unknown blank.
This calculator runs in your browser. Nothing you type is sent anywhere, and no account is needed. If you want to go further than arithmetic — look a structure up, see what a reaction has been recorded as giving, or follow a mechanism — the library is open too.