Percentage Concentration to Molarity Calculator
Convert a percentage concentration to molarity — for weight/volume, weight/weight or volume/volume, including concentrated acids.
The three percentage conventions are not interchangeable.
How the percentage concentration to molarity calculator works
The three percentage conventions are not interchangeable. Weight/volume is grams per 100 mL; weight/weight is grams per 100 g of solution and needs the density; volume/volume is milliliters per 100 mL and needs both density and molar mass.
Concentrated reagents are quoted w/w, which is why converting 37% hydrochloric acid to molarity needs its density of 1.18 kg/L — and gives 12 M, not 10.
Formula: M(w/v) = 10 × % / MM; M(w/w) = 10 × % × ρ / MM
Worked examples
| Inputs | Molarity | Note |
|---|---|---|
| 37% w/w hydrochloric acid | 11.97477 mol/L | 11.97 M |
| 0.9% w/v saline | 0.154 mol/L | 0.154 M |
| 98% w/w sulfuric acid | 18.38499 mol/L | 18.4 M |
FAQFrequently asked questions
What is the difference between w/v and w/w?
Weight/volume is grams per 100 mL of solution; weight/weight is grams per 100 g of solution. They only agree when the density is 1.
How molar is concentrated hydrochloric acid?
About 12 M — 37% w/w at a density of 1.18 kg/L.
How molar is concentrated sulfuric?
About 18.4 M at 98% w/w and 1.84 kg/L. It is by far the most concentrated common reagent.
Why do I need the density for w/w?
Because the percentage is per unit *mass* of solution, and molarity is per unit *volume*. The density converts between them.
Which convention do suppliers use?
Concentrated acids and bases are quoted w/w; laboratory solutions are usually w/v; solvent mixtures are v/v.
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
- National Institute of Standards and Technology — the US measurement and reference-data authority
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.