Mass Concentration to Molar Concentration Calculator 2026-27 — GlobalCalc

GlobalCalc

Inputs

Convert

Mass concentration

g/L

Molar mass

g/mol

Results update as you type

Results

Result

Molarity (mol/L)—

Mass concentration (g/L)—

Mass to weigh out (g)—

Millimolar—

Milligrams per litre—

Moles in that volume—

Reviewed September 2026. Chemistry is the same in every country: SI and laboratory units throughout.

All calculations run 100% in your browser. The calculator code does not submit your figures to GlobalCalc to obtain a result.

About mass concentration to molar concentration

Method

How the mass concentration to molar concentration calculator works

Molarity is mass concentration divided by molar mass: a solution at 40 g/L of a substance with molar mass 40 g/mol is exactly 1 M.

The practical direction is usually the reverse — how much to weigh out. To make 250 mL of 0.1 M from something with molar mass 180, you need 0.1 × 0.25 × 180 = 4.5 g.

Formula: M = (g/L) / molar mass; mass = M × V × molar mass

Data

Worked examples

Inputs	Result	Note
40 g/L at molar mass 40	1	exactly 1 M
0.1 M glucose in 250 mL	18.016	weigh 4.5 g
Back the other way	0.1	0.1 M

FAQ

Frequently asked questions

How do I convert g/L to molarity?

Divide by the molar mass in g/mol.

How much do I weigh out?

Molarity × volume in litres × molar mass. 0.1 M in 250 mL of something at 180 g/mol needs 4.5 g.

What if my compound is hydrated?

Use the molar mass including the water of crystallisation. CuSO₄·5H₂O is 249.7 g/mol, not 159.6 — a 56% error if you get it wrong.

Should I make up to volume or add volume?

Make up to the mark. Dissolving solute changes the volume, so adding a litre of water to the solid does not give a litre of solution.

What about purity?

Divide by the stated purity. A reagent at 95% needs 5% more mass weighed out.

Sources

Where these figures come from

IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
NIST Chemistry WebBook — thermochemical data
Royal Society of Chemistry — the UK chemistry professional body

Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.