Percent Purity Calculator
Find the purity of a chemical sample.
Results update as you type.
How it works
Percent purity tells you how much of a sample is the actual substance you want versus impurities, and this calculator computes it. You enter the mass of the pure substance and the total mass of the sample, and it returns the percent purity and the mass of impurities. The calculation divides the pure mass by the total mass and multiplies by 100. Purity matters enormously in chemistry, pharmaceuticals, food, and manufacturing, because impurities can affect reactions, product quality, safety, and measurements. For instance, a reagent labeled 98 percent pure contains 2 percent other material, which must be accounted for when weighing out precise amounts for a reaction. Chemists often determine the pure mass through analysis such as titration, chromatography, or measuring the yield of a reaction that consumes only the pure component. Higher purity generally commands a higher price and is required for sensitive applications like pharmaceuticals and electronics, while lower purity may be acceptable for industrial bulk uses. Percent purity is also used in reverse: knowing the purity of a starting material lets you calculate how much pure substance a given mass actually provides. Enter the pure mass and total sample mass to find the percent purity.
Percent purity = (pure mass ÷ total sample mass) × 100
Percent purity is the mass of the pure substance divided by the total mass of the sample, multiplied by 100. The remainder is impurities. It tells you what fraction of a sample is the actual substance of interest rather than contaminants or other materials.
Source:Analytical chemistry
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter mass of pure substance and total sample mass.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Percent purity updates instantly as you type — no button to press.
Frequently asked questions
How do you calculate percent purity?
Divide the mass of the pure substance by the total mass of the sample, then multiply by 100. For example, if 45 grams of a 50-gram sample is the pure substance, the purity is 90 percent, leaving 5 grams of impurities. The pure mass is often found through chemical analysis or reaction yield.
Why does purity matter in chemistry?
Impurities can interfere with reactions, skew measurements, reduce product quality, and pose safety risks, so knowing purity is essential. When weighing a reagent, its purity tells you how much actual substance you are adding. In pharmaceuticals, food, and electronics, strict purity standards ensure products are safe and perform as intended, making accurate purity determination critical.
How is the pure mass determined?
The mass of pure substance is usually found by analytical methods such as titration, chromatography, or spectroscopy, or by measuring the yield of a reaction that consumes only the pure component. These techniques separate or quantify the substance of interest apart from impurities, giving the pure mass you then compare to the total sample mass to find purity.
How does purity affect the amount of substance I have?
If a material is not fully pure, a given mass contains less of the actual substance than its weight suggests. For example, 100 grams of a 90 percent pure sample contains only 90 grams of the real substance. Accounting for purity is essential when precise quantities are needed, such as measuring reactants for a reaction.
What purity levels are typical?
Purity requirements vary by use. Industrial bulk chemicals may be 90 to 98 percent pure, laboratory-grade reagents often 98 to 99.5 percent, and pharmaceutical or electronic-grade materials 99.9 percent or higher. Higher purity generally costs more and is reserved for sensitive applications, while lower purity suffices where small amounts of impurities do not affect the outcome.