Molarity (M) is the number of moles of solute dissolved in one liter of solution. It is the most common unit of concentration in chemistry and biology, expressed as mol/L or simply M.

How is molarity calculated from mass?

Molarity = (mass in grams / molar mass in g/mol) / volume in liters. First convert grams to moles by dividing by molar mass, then divide the moles by the solution volume in liters.

Where do I find the molar mass of a compound?

Add the atomic masses of all atoms in the molecular formula. For example, NaCl has a molar mass of 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol. Most reagent bottles and databases list molar mass directly.

What is the difference between molarity and molality?

Molarity is moles of solute per liter of solution (volume-based). Molality is moles of solute per kilogram of solvent (mass-based). This calculator computes molarity only.

Can I enter the volume in milliliters?

Yes. Select mL from the volume unit dropdown and the calculator automatically converts it to liters before computing molarity.

Why does my answer have many decimal places?

The result is displayed to four significant figures. For most lab work, round to the precision of your least accurate measurement (usually two or three significant figures).

Molarity from Mass Calculator

Enter solute mass, molar mass, and solution volume to instantly calculate molarity in mol/L.

Solution Parameters

Fill in all three fields to calculate molarity.

Solute Mass

Molar Mass

g/mol

Solution Volume

Common Molar Masses

Result

Enter values on the left and click Calculate.

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Summary

This tool calculates the molar concentration (molarity) of a solution given the mass of dissolved solute, its molar mass, and the total volume of the solution. Molarity is one of the most fundamental quantities in chemistry and biology, used whenever preparing buffers, reagents, or cell-culture media. Enter your values, choose your unit of volume, and the result appears instantly — no server required.

How it works

Enter the solute mass in grams.
Enter the molar mass of the solute in g/mol.
Enter the solution volume and select the unit (L or mL).
The tool divides mass by molar mass to get moles, then divides by volume in liters to get molarity.
Results display molarity (mol/L), total moles, and the formula used.

Use cases

Prepare a standard solution of known concentration in a chemistry lab.
Verify solution molarity when dissolving a weighed amount of reagent.
Convert grams of a compound to molar concentration for biological assays.
Check stock solution concentration before diluting for cell culture experiments.
Calculate the molarity of a buffer solution prepared from a measured mass of solute.
Teach or verify molarity concepts in academic courses.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu