One way to find a percentage of an amount is to use 1%, 10% and 50% as building blocks. 1%, 10% and 50% can be used as building blocks for working out percentages in your head. 1% is 1⁄100.

When using chemical formula it is possible to calculate the percentage composition of the chemical. This can be useful when extracting metals from ores or when making fertilisers for specific plants.