Molarity Calculator
The Concentration Unit Every Chemist Reaches for First
When a chemist says a solution is "2 molar" or "0.5 M," they're using the most common way of expressing how much solute is packed into a solution — molarity. It's the unit stoichiometry problems are built around, and it converts directly to moles or volume whenever one of the two is known.
The Formula
Molarity = Moles ÷ Volume (L)
Rearranged, this calculator also solves for moles (Moles = Molarity × Volume) or for volume (Volume = Moles ÷ Molarity), depending on which two values are already known.
Where This Calculation Matters
- Recipe conversion in the lab — a procedure calling for "50 mL of 0.1 M HCl" requires converting that into a specific mole count to prepare correctly.
- Stoichiometric reaction planning — molarity and volume together determine exactly how many moles of a reagent are being delivered into a reaction.
- Serial dilution and calibration curves — preparing a set of standards at known molarities is standard practice in analytical chemistry.
- Comparing solution strength — molarity gives an apples-to-apples way to compare the concentration of different reagents.
Worked Examples
| Moles | Volume | Molarity |
|---|---|---|
| 1 mol | 1 L | 1.0 mol/L |
| 0.5 mol | 0.25 L | 2.0 mol/L |
| 2 mol | 4 L | 0.5 mol/L |
How to Use This Calculator
- Choose which value to solve for — molarity, moles, or volume.
- To find molarity, enter Moles of Solute (mol) and Volume of Solution (L).
- To find moles, enter Molarity (mol/L) and Volume of Solution (L) instead; to find volume, enter Molarity (mol/L) and Moles of Solute (mol).
- Select Calculate to get the missing value.
Related Calculations
Need moles from a measured mass first? Start with the Moles Calculator. To dilute a known molarity down to a target concentration, use the Dilution Calculator.