Math Calculators

Subtract the final value from the starting value, divide that by the starting value, then multiply by 100. For a fall from 750 to 590 the difference is 160, 160 ÷ 750 = 0.2133, and the percentage decrease is 21.33%. Always divide by the starting value, never the final one, and keep both numbers in the same unit.

Divide the reduced price by the share that is left, written as a decimal. If a coat costs £60 after 25% off, 75% is left, so the original price is £60 ÷ 0.75 = £80. Adding 25% back onto £60 gives £75, which is wrong because 25% of the sale price is a smaller amount than 25% of the original.

A percentage decrease compares the fall with where the value started. A percentage point decrease is just one percentage subtracted from another. A rate that drops from 5% to 4% has fallen by 1 percentage point, but that is a 20% decrease, because 1 is a fifth of 5. Both statements are true, so say which one you mean.

No. The second decrease is taken from the smaller amount the first one leaves. A 20% decrease followed by another 20% takes 100 to 80 and then to 64, a 36% decrease in total rather than 40%. To combine them, multiply the multipliers (0.8 × 0.8 = 0.64) and take the result away from 1.

Only when the value ends up below zero. A fall to exactly zero is a 100% decrease, and a fall from 200 to −50 is 125%, because the drop of 250 is bigger than the starting 200. For anything that cannot go negative, such as a price or a headcount, a percentage decrease stays between 0% and 100%.