Molarity calculator
Molar concentration of a solution from moles or from a mass.
Fill in the fields and the result will appear here automatically.
Molarity is amount of substance per volume of finished solution. Enter moles, or mass in grams and molar mass in g/mol. Select mL, L or m³ for the volume. The calculation does not identify the substance or check its solubility.
How it works
Formula and logic
C = n/V in litres; mass mode uses n = m/M. 1 mL = 0.001 L and 1 m³ = 1000 L. Divisions are reordered to preserve finite answers when an intermediate conversion overflows. Mass and amount must be finite and nonnegative; volume and molar mass must be finite and positive. Volume is normally shown in litres; if that conversion is outside the numeric range, the original unit is retained.
Example
0.5 mol in 2 L gives 0.25 mol/L. 58.44 g with M = 58.44 g/mol in a final 500 mL gives 1 mol / 0.5 L = 2 mol/L.
Fields and units
- What is known — list option
- Amount of substance, mol — mol
- Mass of substance, g — g
- Molar mass, g/mol — g/mol
- Volume unit — list option
- Solution volume — in the selected volume unit
How to use
- — Choose amount of substance or mass.
- — Enter a finite nonnegative amount; in mass mode enter M in g/mol.
- — Select the volume unit and enter the final volume of the whole solution.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- IUPAC: amount concentration — moles per mixture volume
- Limitation
- The entered final solution volume is used. Temperature, density, activity and solubility are not modelled. Unrepresentable quantities produce an error; displayed values are rounded.
FAQ
Which volume is needed?
The finished solution volume at the chosen temperature. Solvent and solute volumes need not add; a universal volume increase is not assumed.
Can I enter millilitres?
Yes, select mL. 500 mL is treated as 0.5 L, so do not convert the number by hand first.
How does molarity differ from molality?
Molarity divides moles by solution volume. Molality divides by solvent mass in kg; it is not calculated here.
Can I enter a mass percentage?
No. Converting it to mol/L requires a consistent molar mass and solution density. A percentage is not an amount in moles.
Can mass or amount of substance be zero?
Yes. 0 mol in a positive volume gives 0 mol/L; 0 g with positive molar mass and volume also gives 0 mol/L. Losing a positive amount or concentration to zero produces an error.