Common percentage formulas

Finding X% of a value

The basic formula is: X multiplied by Y divided by 100. For instance, 15% of 200 gives 15 x 200 / 100 = 30. This operation comes up daily when calculating tips, discounts or the VAT included in a price.

Finding what percentage X is of Y

The inverse formula is: X divided by Y, multiplied by 100. If you scored 45 marks on a test out of 60, your result is 45 / 60 x 100 = 75%. The same logic applies when working out a budget share or the proportion of an ingredient in a recipe.

Three quick examples

20% of 150 = 30. Useful for calculating à 20% discount on à 150 EUR item.

What percentage is 8 of 200? Answer: 8 / 200 x 100 = 4%. Handy for evaluating an interest rate or a yield.

350 + 5.5% = 369.25. That is the VAT-inclusive price when adding reduced-rate VAT to à 350 EUR base amount.