Mass Percent Calculator
Find the mass percent of a solution.
Results update as you type.
How it works
Mass percent, also called percent by mass or weight percent, is a simple and widely used way to express the concentration of a solution, and this calculator finds it. You enter the mass of the solute (the substance being dissolved) and the mass of the solvent (what it dissolves in), and it returns the mass percent and the total solution mass. The calculation divides the solute mass by the total mass of the solution and multiplies by 100. For example, dissolving 20 grams of salt in 80 grams of water gives a 100-gram solution that is 20 percent salt by mass. Mass percent is popular because it depends only on masses, which are easy to measure precisely and do not change with temperature the way volumes can. It appears on product labels, in chemical recipes, and throughout industry, from food and cosmetics to cleaning products and alloys. Note that the denominator is the total solution mass, solute plus solvent, not just the solvent — a common mistake. Related concentration measures include molarity (moles per liter) and parts per million for very dilute solutions. Enter the solute and solvent masses to find the mass percent.
Mass % = (solute mass ÷ total solution mass) × 100
Mass percent is the mass of the solute divided by the total mass of the solution — solute plus solvent — multiplied by 100. It expresses what fraction of the solution's weight comes from the dissolved substance, a common way to state concentration in labs and industry.
Source:Solution chemistry
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Worked example
How to use this calculator
- 1
Enter your values
Enter solute mass and solvent mass.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Mass percent updates instantly as you type — no button to press.
Frequently asked questions
How do you calculate mass percent?
Divide the mass of the solute by the total mass of the solution, which is the solute plus the solvent, then multiply by 100. For instance, 20 grams of solute in 80 grams of solvent makes a 100-gram solution, so the mass percent is 20 percent. Always use the total solution mass in the denominator.
What is the difference between solute and solvent?
The solute is the substance being dissolved, usually present in the smaller amount, while the solvent is what does the dissolving, usually the larger amount, often water. In salt water, salt is the solute and water is the solvent. Mass percent measures how much of the total solution mass comes from the solute.
Why use the total solution mass, not the solvent mass?
Concentration describes the makeup of the whole solution, so the denominator must be the total mass — solute plus solvent — not just the solvent. Dividing by only the solvent mass overstates the concentration. This is a common error; remember that a 20 percent solution means the solute is 20 percent of the entire mixture's weight.
Why is mass percent commonly used?
Mass percent relies only on masses, which are easy to measure accurately and, unlike volumes, do not change with temperature. This makes it reliable and reproducible. It appears on many product labels and in industrial and lab recipes, from foods and cosmetics to cleaning agents and metal alloys, wherever a straightforward, temperature-independent concentration is useful.
How does mass percent relate to other concentration units?
Mass percent is one of several concentration measures. Molarity expresses moles of solute per liter of solution, molality uses moles per kilogram of solvent, and parts per million suits very dilute solutions. Mass percent is the most intuitive for everyday mixtures, while molarity is preferred for reactions since it counts particles rather than weight.