Molarity Calculator
Calculate molarity, solute mass, or solution volume — solve M = n/V for whichever quantity you're missing, given a molar mass and the other two values.
Input
Grams per mole of the solute. Use the Molar Mass Calculator to derive it from a formula.
Output
| Metric | Value |
|---|---|
| No data yet | |
Guides
The Molarity Calculator solves for molarity, solute mass, or solution volume — pick the quantity you're missing, supply the other two plus a molar mass, and it derives the rest.
What is molarity?
Molarity (M), or molar concentration, is the number of moles of solute dissolved per liter of solution:
M = n ÷ Vwhere n is moles and V is volume in liters. Moles themselves come from mass and molar mass:
n = mass ÷ molar massCombining the two gives the full relationship this calculator solves:
M = mass ÷ (molar mass × V)How to use it
- Pick what you want to Solve For — Molarity, Solute Mass, or Solution Volume.
- Enter the Molar Mass of the solute in g/mol — this is always required, since it's what converts mass into moles. Don't know it? Use the Molar Mass Calculator to derive it from a chemical formula first.
- Fill in the other two fields (whichever weren't hidden by your solve-for choice).
The calculator shows the solved value along with molarity, solute mass, molar mass, solution volume, and moles all together, plus a short step-by-step derivation.
Example
Dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in enough water to make 1 L of solution gives:
n = 58.44 g ÷ 58.44 g/mol = 1 mol
M = 1 mol ÷ 1 L = 1 mol/LThat's a 1 M (one molar) sodium chloride solution.
Does volume mean the volume of solvent I add, or the final solution?
The final solution volume — after the solute is fully dissolved and the solution is brought up to that volume, not just the water added beforehand. This matters because dissolving a solute changes the total volume slightly.
What if I have a percentage concentration instead of a mass?
Convert it to a mass first (percentage × total solution mass), then use this calculator. Molarity is a moles-per-volume measure, not a mass-fraction measure.
Privacy
All calculations run entirely in your browser. Your figures are never uploaded or stored.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/molarity-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"solveFor": "molarity",
"mass": "58.44",
"molarMass": "58.44",
"volume": "1",
"molarity": "1"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `molarity-calculator` tool (Molarity Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.