Quick answer
Mass percent = mass of component ÷ total mass × 100. 12 g of solute in 100 g of solution is 12%.
Enter the component mass and the total mass. The calculator returns the mass percent.
Related tools: Percent Yield Calculator: Percent yield of a reaction. Molar Mass Calculator: Molar mass and mass percent composition of a chemical formula. Average Atomic Mass Calculator: Weighted average of isotope masses.
How to use the Mass Percent Calculator
- Enter mass of component (above 0).
- Enter total mass (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Mass of component | A number | > 0 |
| Total mass | A number | > 0 |
Formula and method
Formula
mass % = component ÷ total × 100
IEEE-754 double precision; shown to the decimals indicated.
Use the same unit for both.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Mass of component = 12; Total mass = 100.
| Result | Value |
|---|---|
| Mass percent | 12% |
Example 2
Inputs: Mass of component = 35.5; Total mass = 58.44.
| Result | Value |
|---|---|
| Mass percent | 60.7461% |
Example 3
Inputs: Mass of component = 0.9; Total mass = 100.
| Result | Value |
|---|---|
| Mass percent | 0.9% |
The first line is the headline result (mass percent). IEEE-754 double precision; shown to the decimals indicated.
Concentration by mass
A 12% by mass solution has 12 g of solute per 100 g of solution, with 88 g of solvent. The total includes the solute. Mass percent does not change with temperature.
Related ideas
Mass percent is also called weight percent (w/w). For a solution of 12 g salt in 88 g water, the total is 100 g. The component can't exceed the total.
How the result changes with mass of component
Holding every other input at the first worked example, this table changes only mass of component. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Mass of component | Mass percent |
|---|---|
| 6 | 6% |
| 12 | 12% |
| 24 | 24% |
| 48 | 48% |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Mass of component: entering "0" shows "Mass of component must be greater than 0." beside that field and no result.
Choosing between the Mass Percent Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Percent Yield Calculator](/science/percent-yield/) | actual yield and theoretical yield | Percent yield |
| [Molar Mass Calculator](/science/molar-mass-calculator/) | chemical formula | Molar mass |
| [Average Atomic Mass Calculator](/science/average-atomic-mass/) | isotope masses and abundances | Average atomic mass |
| [Mole Calculator](/science/mole/) | start from and molar mass | Amount |
| [Electron Configuration Calculator](/science/electron-configuration/) | element and charge | Electron configuration of H |
Background: chemistry calculations
Most basic chemistry calculations chain three relations: moles n = mass ÷ molar mass, molarity M = n ÷ volume in litres, and dilution C₁V₁ = C₂V₂. Keep units consistent: grams with g/mol, litres with mol/L.
Molar masses come from standard atomic weights, which differ slightly between tables and with the isotopic make-up of a real sample.
Assumptions and limitations
- Component cannot exceed total
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for mass of component to confirm this.
Frequently asked questions
How much solute in 250 g of 12% solution?
250 g × 12% = 30 g of solute, with 220 g of solvent.
What is the difference from molarity?
Molarity uses moles per litre.
Is w/w the same as mass percent?
Yes. w/w (weight per weight) percent and mass percent mean the same thing.
What does the Mass Percent Calculator calculate?
Mass percent of a component in a mixture or compound. It returns Mass percent.
What formula does the Mass Percent Calculator use?
mass % = component ÷ total × 100. Use the same unit for both.
What do I need to enter in the mass Percent Calculator?
You enter Mass of component and Total mass.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Component cannot exceed total.
What is an example of a mass Percent result?
With mass of component 12 and total mass 100, the mass percent is 12%.
Related calculators
- Percent Yield Calculator — Percent yield of a reaction.
- Molar Mass Calculator — Molar mass and mass percent composition of a chemical formula.
- Average Atomic Mass Calculator — Weighted average of isotope masses.
- Mole Calculator — Convert between mass, moles and number of particles.
- Electron Configuration Calculator — Ground-state electron configuration of an element or monatomic ion, with noble-gas shorthand and unpaired electrons.
- Center of Mass Calculator — Center of mass of point masses in one or two dimensions.
- Molality Calculator — Molality of a solution.
Sources
- OpenStax, University Physics Volume 1 (Rice University): mechanics
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.