When a powder is not entirely the analyte of interest, its weighed mass differs from active analyte mass. Enter a target mg/mL, measured final solution volume and assay purity by mass to calculate the mass to weigh.

Formula: analyte mg = target mg/mL × final solution mL; powder mg = analyte mg ÷ (purity % ÷ 100); non-analyte mg = powder mg − analyte mg

Worked example

For 10 mg/mL analyte in a final measured 100 mL, 1,000 mg of analyte is needed. If powder is 95% analyte by mass, weigh about 1,052.63 mg (1.05263 g); about 52.63 mg of that powder is other material.

Assay purity is a mass fraction

Enter the fraction of the weighed powder that is the analyte on the same chemical basis as the target. OpenStax defines mass percentage as component mass divided by total mass. If the assay is on a dry basis or a salt-equivalent basis, convert it appropriately before using this simple calculator.

Use final measured volume

Final solution volume is the total after dissolving and bringing to volume, not the amount of solvent initially added. Powder displacement, incomplete dissolution and losses can make the actual concentration differ from this ideal mass balance.

Laboratory arithmetic only

The result does not determine a dose, assess drug suitability, check solubility, approve a formulation or give preparation instructions. Confirm substance identity, assay basis and any safety requirements independently. Inputs stay in this browser.

Explore the related calculation

For a different starting point, try the mg/mL dilution calculator or return to the main calculator. Browse the complete tool directory for this site.

Reference and corrections

The definitions and assumptions above follow these sources; the examples and calculator arithmetic are original to this page.

openstax.org reference

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Powder purity solution calculator

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