Percentage of Mass is defined as grams of the solute per grams of the solution with 100 percent solution. To calculate Mass Percentage of Chemicals divide Grams of Solute by Grams of Solution and multiply it by 100 to give a percentage. Given below, an online Percent of Mass Calculator to calculate Percentage of a solution by mass. Just enter Grams of Solute and Grams of Solvent in grams to calculate Percentage of Mass with given mass values.