Weight/volume percent (w/v %) expresses grams of solute per 100 mL of solution. For example, 5 w/v % means 5 g of solute dissolved in enough solvent to make 100 mL of solution.

Weight/weight percent (w/w %) expresses grams of solute per 100 g of solution. It is independent of temperature because mass does not change with temperature, unlike volume.

Why do I need the solution density?

Molarity is expressed per liter of solution (volume-based), while w/w percent is mass-based. Converting between them requires the solution density to relate volume to mass.

What density should I use for dilute aqueous solutions?

For dilute aqueous solutions (below ~5% concentration), 1.00 g/mL is a good approximation. For concentrated solutions (acids, bases, salts), use the value from the product SDS or a density table.

What is the formula for w/v percent from molarity?

w/v % = (M × MW) / 10, where M is molarity in mol/L and MW is molecular weight in g/mol. This gives grams per 100 mL.

What is the formula for w/w percent from molarity?

w/w % = (M × MW) / (ρ × 10), where ρ is solution density in g/mL. Equivalently, w/w % = (w/v %) / (ρ × 100) × 100, which simplifies to (M × MW) / (ρ × 10).

Molarity to Mass Percent Converter

Enter molarity, solute molecular weight, and solution density to get mass/volume percent (w/v %) and weight/weight percent (w/w %).

Input Values

Molarity (mol/L)

Molar concentration of the solution

Molecular Weight (g/mol)

Molar mass of the solute

Solution Density (g/mL)

Required only for w/w % calculation

Mass/Volume Percent

w/v %

—

grams of solute per 100 mL of solution

Formula: w/v % = (M × MW) / 10

Weight/Weight Percent

w/w %

—

grams of solute per 100 g of solution

Formula: w/w % = (M × MW) / (ρ × 10)

Common Aqueous Solutions — Reference

Solute	MW (g/mol)	Molarity (mol/L)	Density (g/mL)	w/w %
NaCl (saline)	58.44	0.154	1.005	—
NaOH	40.00	1.00	1.04	—
H₂SO₄ (conc.)	98.08	18.00	1.84	—
HCl (conc.)	36.46	12.00	1.19	—
Glucose	180.16	0.278	1.01	—

Summary

This converter calculates mass/volume percent (w/v %) and weight/weight percent (w/w %) from a solution's molar concentration. Provide the molarity in mol/L, the solute's molecular weight in g/mol, and the solution density in g/mL. The tool applies standard stoichiometric formulas used in analytical and preparative chemistry.

How it works

Enter the solution molarity in mol/L.
Enter the solute molecular weight in g/mol (check the periodic table or SDS sheet).
Enter the solution density in g/mL (water is 1.00 g/mL; concentrated acids are higher).
The w/v percent is computed as (molarity × MW) / 10.
The w/w percent is computed as (molarity × MW) / (density × 1000) × 100.
Click Calculate (or press Enter) to display results.

Use cases

Convert a 1 M NaCl stock solution concentration to mass/volume percent for a reagent label.
Verify the stated percent concentration on a bottle of concentrated sulfuric acid.
Prepare buffer solutions requiring a specific w/w percent from a known molarity.
Cross-check reagent purity between two different concentration units.
Convert between units when a protocol specifies percent but stock is labeled in molarity.
Teaching solution concentration conversions in analytical chemistry coursework.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu