Molarity Calculator
This free molarity calculator finds the molar concentration of a solution — moles of solute per liter of solution — or solves for moles, mass, or volume when you know the others. Molarity is the most common way to express concentration in chemistry, essential for preparing solutions and running reactions. Enter the values you have and the calculator returns the unknown.
How to Use the Molarity Calculator
- Choose what to solve for — molarity, moles, mass, or volume.
- Enter the known values (and molar mass if using mass).
- Calculate — see the result.
The Molarity Formula
Molarity (M) = Moles of Solute ÷ Liters of Solution
For example, dissolving 0.5 moles of a compound in 2 liters of solution gives a molarity of 0.25 M. If you start from mass, first convert to moles using moles = mass ÷ molar mass.
Rearranged Forms
| Solve For | Formula |
|---|---|
| Molarity | moles ÷ volume (L) |
| Moles | molarity × volume (L) |
| Volume | moles ÷ molarity |
| Mass | moles × molar mass |
Preparing a Solution
To make a solution of a target molarity, calculate the moles needed (molarity × volume), convert to grams using the molar mass, weigh out that amount, and dissolve it in solvent up to the final volume. The calculator gives you the exact mass to weigh, which is the most common lab use.
Why Molarity Matters
- Standard unit for concentration in chemistry.
- Required for stoichiometry and reaction calculations.
- Used to prepare reagents and dilutions accurately.
- Connects mass, moles, and volume in one framework.
Frequently Asked Questions
How do you calculate molarity?
Divide the moles of solute by the volume of solution in liters. 0.5 moles in 2 liters is 0.25 M.
What is molarity?
Molarity is the concentration of a solution expressed as moles of solute per liter of solution, written with the unit M.
How do I find moles from mass?
Divide the mass by the molar mass: moles = mass ÷ molar mass. Then use moles and volume to find molarity.
How do I make a solution of a certain molarity?
Multiply the target molarity by the volume to get moles, convert to grams using the molar mass, weigh that amount, and dissolve to the final volume.
Is this molarity calculator free?
Yes — it is completely free, requires no signup, and solves for molarity, moles, mass, or volume.