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Methylene blue
molarity calculator

Convert weighed material and final solution volume into a laboratory concentration. Choose the documented material and assay basis first.

This tool calculates analytical amount concentration. It does not select a human or animal dose, establish solubility, or verify the contents of a sample. All calculations run locally in your browser.

1. Mass and final volume
Volume after dissolution, not solvent volume added.
2. Material and calculation basis
Use the certificate's reporting basis. Unknown hydration is usable only with an as-is or dried-basis anhydrous-equivalent assay.

Calculated concentration

Enter mass and volume, then select the material and calculation basis.

Equations and units

Nominal: c = m / (M × V)
As-is selected form: c = m × a / (M × V)
As-is anhydrous equivalent: c = m × a / (319.85 × V)
Dried basis: c = m × (1 − d) × a / (319.85 × V)

m is mass in grams; V is final volume in litres; M is the selected form's molar mass in g/mol; a is assay divided by 100; d is matching loss on drying divided by 100. The two anhydrous-equivalent modes already account for material composition through the assay. They do not apply an additional hydrate correction.

The dried-basis mode accepts assay estimates above 100% through 103%, consistent with the range in the cited USP preview. These are analytical estimates, not literal mass fractions. Other assay conventions require a separate documented calculation. Five significant figures in the display do not establish measurement precision.