Quick answer
Molarity is moles of solute per litre of solution: M = (mass ÷ molar mass) ÷ volume. Dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in a final volume of 1 L gives 1 mol/L.
Enter the solute mass, molar mass and solution volume. The calculator returns the molarity and moles.
Related tools: Mole Calculator: Convert between mass, moles and number of particles. Percent Yield Calculator: Percent yield of a reaction. Electron Configuration Calculator: Ground-state electron configuration of an element or monatomic ion, with noble-gas shorthand and unpaired electrons.
How to use the Molarity Calculator
- Enter solute mass (g) (above 0).
- Enter molar mass (g/mol) (above 0).
- Enter solution volume (L) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Solute mass | A number, in g | > 0 |
| Molar mass | A number, in g/mol | > 0 |
| Solution volume | A number, in L | > 0 |
Formula and method
Formula
M = (mass ÷ molar mass) ÷ volume
IEEE-754 double precision; shown to at most 6 decimal places.
Moles of solute divided by litres of solution.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Solute mass = 58.44; Molar mass = 58.44; Solution volume = 1.
| Result | Value |
|---|---|
| Molarity | 1 mol/L |
| Moles | 1 |
Example 2
Inputs: Solute mass = 10; Molar mass = 40; Solution volume = 0.5.
| Result | Value |
|---|---|
| Molarity | 0.5 mol/L |
| Moles | 0.25 |
The first line is the headline result (molarity). Below it the molarity Calculator lists moles, which describe the same case from other angles. IEEE-754 double precision; shown to at most 6 decimal places.
Final volume
Use the final solution volume, not the volume of solvent added. To make 1 M NaCl, dissolve the salt in less water, then top up to the 1 L mark in a volumetric flask.
Quick use
For 0.1 M NaCl in 500 mL, you need 0.05 mol = 2.92 g. Molarity changes slightly with temperature because volume does; molality doesn't.
How the result changes with solute mass
Holding every other input at the first worked example, this table changes only solute mass. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Solute mass | Molarity | Moles |
|---|---|---|
| 29.22 | 0.5 mol/L | 0.5 |
| 58.44 | 1 mol/L | 1 |
| 116.9 | 2.000342 mol/L | 2.000342 |
| 233.8 | 4.000684 mol/L | 4.000684 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Molar mass: entering "0" shows "Molar mass must be greater than 0." beside that field and no result.
Choosing between the Molarity Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Mole Calculator](/science/mole/) | start from and molar mass | Amount |
| [Percent Yield Calculator](/science/percent-yield/) | actual yield and theoretical yield | Percent yield |
| [Electron Configuration Calculator](/science/electron-configuration/) | element and charge | Electron configuration of H |
| [Dilution Calculator](/science/dilution-ratio/) | solve for | Final volume V₂ |
| [Average Atomic Mass Calculator](/science/average-atomic-mass/) | isotope masses and abundances | Average atomic mass |
Background: chemistry calculations
Most basic chemistry calculations chain three relations: moles n = mass ÷ molar mass, molarity M = n ÷ volume in litres, and dilution C₁V₁ = C₂V₂. Keep units consistent: grams with g/mol, litres with mol/L.
Molar masses come from standard atomic weights, which differ slightly between tables and with the isotopic make-up of a real sample.
Assumptions and limitations
- Use the final solution volume
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for molar mass to confirm this.
Frequently asked questions
What is 1 M?
A 1 M solution holds one mole of solute per litre of solution, e.g. 58.44 g of NaCl made up to 1 L.
How do I find mass from molarity?
mass = M × V × molar mass.
How do I convert to molality?
You need the solution density.
What does the Molarity Calculator calculate?
Concentration of a solution from solute mass, molar mass and volume. It returns Molarity and Moles.
What formula does the Molarity Calculator use?
M = (mass ÷ molar mass) ÷ volume. Moles of solute divided by litres of solution.
What do I need to enter in the molarity Calculator?
You enter Solute mass (g), Molar mass (g/mol) and Solution volume (L).
How is the result rounded or limited?
IEEE-754 double precision; shown to at most 6 decimal places. Use the final solution volume.
What is an example of a molarity result?
With solute mass 58.44, molar mass 58.44 and solution volume 1, the molarity is 1 mol/L.
Related calculators
- Mole Calculator — Convert between mass, moles and number of particles.
- Percent Yield Calculator — Percent yield of a reaction.
- Electron Configuration Calculator — Ground-state electron configuration of an element or monatomic ion, with noble-gas shorthand and unpaired electrons.
- Average Atomic Mass Calculator — Weighted average of isotope masses.
- Partial Pressure Calculator — Partial pressure of a gas in a mixture (Dalton's law).
Sources
- OpenStax, University Physics Volume 1 (Rice University): mechanics
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.