How to Calculate Percentage — Every Type Explained Simply

Percentages appear everywhere — sale prices, tax rates, pay rises, statistics, nutrition labels, exam scores. Yet many people find certain types of percentage calculations confusing. This guide covers every common type clearly, once and for all.

Type 1: What Is X% of Y?

The most common type. "What is 15% of 80?"

Method: Multiply the number by the percentage divided by 100.
15% of 80 = 80 × 0.15 = 12

Quick mental trick: 10% of any number is just move the decimal point left one place. 10% of 80 = 8. Then half of that for 5% = 4. Add them: 15% = 12.

Type 2: What Percentage Is X of Y?

"12 is what percentage of 80?"

Method: Divide X by Y then multiply by 100.
12 ÷ 80 × 100 = 15%

Type 3: Percentage Change

"A price went from £40 to £52. What is the percentage increase?"

Method: (New − Old) ÷ Old × 100.
(52 − 40) ÷ 40 × 100 = 12 ÷ 40 × 100 = 30% increase

For a decrease, the result will be negative. A drop from £52 to £40 is (40−52)÷52×100 = −23.1% — note this is a different percentage to the increase, which surprises many people.

Type 4: Adding a Percentage (e.g. VAT)

"Add 20% VAT to £150."

Method: Multiply by (1 + percentage/100).
£150 × 1.20 = £180

Type 5: Removing a Percentage (e.g. Removing VAT)

"A price of £180 includes 20% VAT. What is the pre-VAT price?"

Method: Divide by (1 + percentage/100).
£180 ÷ 1.20 = £150

Common mistake: subtracting 20% of £180 (which gives £144, not £150). Always divide, never subtract, when removing a percentage that was added.

Type 6: Reverse Percentage

"After a 25% increase, a price is £250. What was the original?"

Method: Divide by (1 + percentage/100).
£250 ÷ 1.25 = £200