Standard Solution & Dilution Calculator (Purity and Salt Correction)

Get the true stock concentration and the aliquot for your working standard.

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Weight of reference standard mg

Purity (as is) %

MW of salt form (optional) g/mol

MW of free base (optional) g/mol

Stock volume mL

Target working conc. µg/mL

Working volume mL

Example: 25.40 mg into 25 mL, diluted to a 50 µg/mL working standard. Fill both MWs to express the result as the free base.

Stock conc.–

Aliquot of stock–

Dilution factor–

C_stock = W·P·(MW_base/MW_salt)/V · V_aliquot = C_target·V_target/C_stock

How it works

The concentration of a reference standard solution depends on the weight, the purity on the as-is basis and, for salts, the ratio of the free-base and salt molecular weights. Getting these right matters more than the number of decimal places on the balance.

Very small aliquots carry larger relative error. If the aliquot falls below about 0.5 mL, an intermediate dilution usually gives a more accurate working standard.