Mass Percent Solution Calculator
w/w, w/v and v/v — which are not interchangeable.
w/w, w/v and v/v — which are not interchangeable. Pick the convention, enter the solute and the total solution, and this returns the percentage.
Grams for w/w and w/v, millilitres for v/v.
The TOTAL, not the solvent. 10 g of salt in 100 g of water makes 110 g of solution.
Concentration, w/w
9.091%
% by mass (g solute per 100 g solution)
The denominator is the solution, not the solvent, and this is where most of the error in the calculation lives. Dissolving 10 g of salt in 100 g of water gives 110 g of solution and 9.09% w/w — not 10%. The three conventions are not interchangeable. w/w is grams per 100 g of solution, w/v is grams per 100 mL, and v/v is millilitres per 100 mL. They coincide only for dilute aqueous solutions where density is close to 1 g/mL; for concentrated acids or anything organic they diverge substantially. A bottle labelled simply "5% solution" is ambiguous. Pharmacopoeial convention treats it as w/v for a solid in a liquid and v/v for a liquid in a liquid, but it is worth confirming rather than assuming.
How the Mass Percent Solution Calculator works
Pick the convention, enter the solute and the total solution, and this returns the percentage. The denominator is the solution rather than the solvent, which is where most of the error in this calculation lives: 10 g of salt in 100 g of water is 9.09% w/w, not 10%.
Also known as: w/v percent calculator · percent by mass calculator for solutions · how to make a 5 percent solution · v/v percent calculator
Where to go next
The Mass Percent Solution question rarely arrives on its own. These are the ones that usually come with it:
- Molarity Calculator — Moles per litre of solution — not of solvent.
- PPM Calculator — Parts per million, with the mg/L approximation named.
- Dilution Calculator — M₁V₁ = M₂V₂, with the diluent volume you actually need.
- Osmolarity Calculator — Counts particles, so 0.154 M saline is 308 mOsm/L.
Frequently asked questions
How do I calculate mass percent?
Divide the mass of solute by the mass of the whole solution and multiply by 100. Note that the solution is solute plus solvent, not the solvent alone.
What is the difference between w/w, w/v and v/v?
w/w is grams per 100 g of solution, w/v is grams per 100 mL of solution, and v/v is millilitres per 100 mL. They agree only for dilute aqueous solutions where density is near 1 g/mL.
How do I make a 5% solution?
For 5% w/v, dissolve 5 g in enough solvent to reach 100 mL total — not 5 g in 100 mL of solvent. Making up to volume is the step that gets skipped.
What does an unlabelled percentage mean?
It is genuinely ambiguous. Pharmacopoeial convention reads it as w/v for a solid in a liquid and v/v for a liquid in a liquid, but for anything concentrated it is worth confirming rather than assuming.
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Related calculators
Molarity Calculator
Moles per litre of solution — not of solvent.
OpenPPM Calculator
Parts per million, with the mg/L approximation named.
OpenDilution Calculator
M₁V₁ = M₂V₂, with the diluent volume you actually need.
OpenOsmolarity Calculator
Counts particles, so 0.154 M saline is 308 mOsm/L.
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