Mass Percentage
The mass of solute expressed as a percentage of the total mass of the solution.
Formula / equation
% w/w = (m_solute / m_solution) × 100
Unit
Dimensionless
In depth
Mass percentage is temperature-independent and requires no knowledge of molar mass, which makes it convenient for commercial products and for mixtures of ill-defined composition. It is the standard way concentrated acids and alloy compositions are quoted.
Examples in the real world
Concentrated sulfuric acid is 98% w/w; an 18-carat gold alloy is 75% gold by mass.