Home › Chemistry › Mass Percent Calculator

Mass Percent Calculator

Computes the mass percent (% w/w) of a solute from the solute mass and either the total solution mass or the solvent mass, and expresses the same concentration as mass fraction, parts per million and parts per billion.

When to use

You need the % w/w, ppm or ppb concentration of a solute in a solution or mixture from masses.

Do not use when: You need molarity (mol/L, use molarity), the percent composition of an element within a compound (use molar-mass), or volume-based units such as % v/v.

Formula

mass_percent = 100 × solute_mass / solution_mass, where solution_mass = solute_mass + solvent_mass; ppm = 10⁶ × solute_mass / solution_mass; ppb = 10⁹ × solute_mass / solution_mass

Inputs

Parameter	Type	Required	Description
`solute_mass`	number	yes	Mass of the solute in any unit shared by all masses (g, kg, mg). Range: > 0
`solvent_mass`	number	no	Mass of the solvent; solution mass = solute + solvent. Ignored when solution_mass is given. Range: ≥ 0
`solution_mass`	number	no	Total mass of the solution (solute + solvent). Use this when the total, not the solvent, is known. Range: > 0

Outputs

Output	Type	Unit	Description
`mass_percent`	number	% w/w	100 × solute_mass / solution_mass.
`mass_fraction`	number		solute_mass / solution_mass.
`ppm`	number	ppm	10⁶ × mass fraction (mg per kg of solution).
`ppb`	number	ppb	10⁹ × mass fraction (µg per kg of solution).
`solution_mass`	number		Total mass of the solution, in the input unit.
`solvent_mass`	number		solution_mass − solute_mass, in the input unit.

Example

5 g NaCl in 95 g water: {"solute_mass":5,"solvent_mass":95} → {"mass_percent":5,"mass_fraction":0.05,"ppm":50000,"ppb":50000000,"solution_mass":100,"solvent_mass":95}

2 mg of lead in 1 kg of solution: {"solute_mass":0.002,"solution_mass":1000} → {"mass_percent":0.0002,"ppm":2,"ppb":2000,"solvent_mass":999.998}

GET https://tttkmbb.com/api/v1/calculate/mass-percent?solute_mass=5&solvent_mass=95

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/mass-percent (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/mass-percent · Markdown: https://tttkmbb.com/chemistry/mass-percent.md · JSON definition: https://tttkmbb.com/chemistry/mass-percent.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="mass-percent"
OpenAPI operationId: calculate_mass_percent
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

OpenStax Chemistry 2e – 3.4 Other Units for Solution Concentrations (textbook)
Wikipedia – Mass fraction (chemistry) (reference)

FAQ

Is the denominator the solvent or the whole solution?

The whole solution (solute + solvent). 5 g of salt in 95 g of water is 5% w/w, not 5.26%.

Is 1 ppm the same as 1 mg/L?

Only for dilute aqueous solutions whose density is about 1 kg/L; ppm here is strictly mass-based (mg of solute per kg of solution).

Related calculators

Molarity Calculator — Molar concentration instead of mass-based concentration.
Dilution Calculator — Dilute the solution to a lower concentration.
Percentage Calculator — General percentage arithmetic.