Percent Concentration to Molarity Calculator

Convert a weight-percent solution (with its density) into molarity.

How the Math Works

The formula M = (10 × % × density) ÷ molar mass converts percent concentration (w/w) to molarity by accounting for the relationship between mass, volume, and molecular mass. Here, the '10' arises from simplifying unit conversions: dividing by 100 (to convert % to a decimal) and multiplying by 1000 (to convert mL to liters), resulting in 1000/100 = 10. The density (in g/mL) bridges mass and volume, allowing the calculation of solute mass per liter of solution, which is then divided by molar mass to yield moles per liter (molarity).

Practical Applications

This calculator is essential in laboratory settings for preparing accurate chemical solutions. For example, if a protocol requires a 15% NaCl solution with a density of 1.1 g/mL and a molar mass of 58.44 g/mol, the formula quickly computes the molarity (approximately 2.8 M), ensuring precise reagent concentrations for experiments, titrations, or quality control tests.

Day-to-Day Use

In everyday scenarios, this tool helps with tasks like mixing cleaning solutions, cooking concentrates, or adjusting pool chemicals. For instance, a 10% hydrogen peroxide solution (density 1.11 g/mL, molar mass 34.01 g/mol) converts to ~3.26 M, guiding safe and effective dilution for disinfection or hair bleaching. It empowers users to translate common percentage labels into actionable molarity values for reliable results.

Worked example

37% HCl, density 1.19, M 36.46 → ~12.1 M.

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