How do you convert percentages to masses?

You assume a 100 g sample, and the masses are then numerically the same as the percentages.

Are you talking about empirical formula calculations, where you have to convert the percentages to masses?

For example, a compound may contain 50.05 % sulfur and 49.95 % oxygen by mass.

You first have to convert these percentages to masses.

You should assume a total mass of exactly 100 g.

In mathematics, a percentage is a decimal fraction.

##”Decimal Fraction” = %/100##

So, 40.05 % = 0.4005, and 49.95 % = 0.4995

To get the mass, you multiply the total mass by the decimal fraction.

Mass of S = 0.4005 × 100 g = 40.05 g. Mass of O = 0.4995 × 100 g = 49.95 g

If you use conversion factors in your chemical calculations, you can write

##”Mass of S” = cancel(“100 g sample”) × “40.05 g S”/cancel(“100 g sample”) = “40.05 g S”##

##”Mass of O” = cancel(“100 g sample”) × “49.95 g O”/cancel(“100 g sample”) = “49.95 g O”##

Either method is quite acceptable. Use the one that you prefer.