Chemistry & Lab tools
Percent purity calculator
Weigh the active ingredient against the total sample, and know exactly how much of what you bought is actually what you paid for.
Formula
Purity % = (Active Ingredient Mass ÷ Total Sample Mass) × 100
Sample
Total sample weight
Full weight of the sample as received
g
Active ingredient weight
Weight of the pure active substance, from assay
g
Purity
0%
Impurity–
Impurity mass–
Active vs. impurity content
When purity is lower than expected, scale up the raw material weight accordingly in any downstream dosage or formulation calculation — a formulation designed for 99% purity input will under-deliver active ingredient if fed material that’s actually 92% pure, unless the recipe is adjusted for the difference.
Frequently asked questions
What is percent purity?
The proportion of a sample that consists of the actual active substance, as opposed to impurities, water, or filler, expressed as a percentage of total sample weight.
How do I calculate percent purity?
Divide the mass of pure active ingredient by total sample mass, then multiply by 100. 95g active in a 100g sample gives 95% purity.
Why does purity matter for dosage?
Lower purity means more of the total mass is inert material, so you need a larger total weight of raw material to deliver the same active ingredient in a dose.
Is this percent purity calculator free to use?
Yes. It runs entirely in your browser, needs no account, and nothing you enter is stored or transmitted.