โ† Lab Calculator Free ยท No sign up ยท Instant

๐Ÿ”ฌ Purity & Potency Calculator

Calculate the corrected weight to weigh based on purity percentage or potency value of your reference standard.

Corrected Weight = Required Weight รท (Purity% รท 100)
%
From Certificate of Analysis (CoA)
Corrected Weight to Weigh
โ€”
๐Ÿ’ก Why this matters: Reference standards are never 100% pure. A standard labelled 99.2% purity means for every 100 mg you weigh, only 99.2 mg is the actual compound. Always apply purity correction to avoid systematic errors in your analytical results.
โš ๏ธ Verify before use: Double-check critical weighing calculations independently, especially for regulated or validated methods.
๐Ÿ“– Example (Purity mode): You need 10 mg of a reagent with stated purity 97.5%. Adjusted mass to weigh = 10 รท 0.975 = 10.26 mg. Report in thesis: "10 mg (adjusted for purity, actual mass weighed: 10.26 mg)."
๐Ÿ“œ

CoA-based

Uses the purity or potency value directly from your Certificate of Analysis.

โœ…

ICH compliant

Purity correction is a required step in ICH Q2(R1) method validation.

๐Ÿ†“

Always free

No sign up, no limits. Use for every standard preparation.

โœ” Formulas last verified against primary references: March 2025  ยท  Report an error
โš ๏ธ Report an incorrect calculation

Frequently asked questions

Why do I need to correct for purity when weighing a reagent?

Reference standards and reagents are rarely 100% pure โ€” a certificate of analysis might state 98.5% purity, meaning 1.5% of the weighed mass is inert impurity, not active compound. If you weigh the simple stoichiometric mass without correction, you'll actually add less active compound than intended.

What's the difference between purity and potency?

Purity typically refers to the fraction of a substance that is the intended chemical compound (vs. impurities or residual solvent). Potency is a broader term sometimes used for biological or complex materials, expressing activity relative to a reference standard, which may not be a simple chemical purity percentage โ€” check your certificate of analysis for which value applies.

Where do I find the purity or potency value for my reagent?

This is stated on the reagent's certificate of analysis (CoA), typically supplied by the manufacturer with each lot. Purity can vary between lots of the same product, so always use the CoA for your specific lot rather than a generic label value.

Accuracy & how this is derived

Derivation: Adjusted mass is calculated as target mass divided by the fractional purity (purity%/100), so that the actual amount of active compound delivered matches the intended target mass despite the reagent containing some fraction of inert material.

Validated against: Standard purity correction methodology used in analytical chemistry and pharmaceutical reference standard preparation (e.g. as referenced in USP General Chapter <11>).

โš ๏ธ For educational and research support only โ€” verify critical results independently before use in regulated, clinical, or publication-bound work.

โœ” Last updated: July 2026  ยท  Report an error

Try next โ†’
๐Ÿ’ง Simple Dilution Calculatorโš–๏ธ Concentration Converter๐Ÿ“ˆ Yield Calculator

Correcting for reagent purity in gravimetric preparation

Analytical grade reagents rarely achieve 100% purity. A 97.5% stated purity means 2.5% of every weighed mass is impurity or solvent of crystallisation. Adjusted mass = desired mass รท (purity/100). For enzyme and antibody preparations, activity units rather than mass purity are used โ€” 1 Unit is typically the amount of enzyme that catalyses the conversion of 1 ยตmol of substrate per minute under defined conditions. Always record lot number and stated activity/purity from the CoA in your lab notebook.