7 Percentage Calculations You'll Actually Use in Everyday Life

Percentages are one of those maths skills that quietly show up everywhere — shopping, restaurants, payslips, savings accounts. Knowing a few core calculations saves you from reaching for a calculator every time.

1. Finding a percentage of a number

To find X% of Y, divide X by 100 and multiply by Y. A 20% tip on a $45 bill is (20/100) × 45 = $9.

2. Finding what percentage one number is of another

Divide the part by the whole and multiply by 100. If you scored 42 out of 50 on a test, that's (42/50) × 100 = 84%.

3. Percentage change

Subtract the old value from the new value, divide by the old value, and multiply by 100. This works for price increases, salary raises, or tracking any metric over time.

4. Discounts

A 30% discount on a $80 item means you pay 70% of the price: 0.7 × 80 = $56.

5. Reverse percentages

If a price already includes a 20% markup and you want the original price, divide by 1.2 rather than subtracting 20%.

6. Compound percentage changes

Two 10% increases in a row are not the same as a 20% increase — because the second increase applies to the already-increased number, the combined effect is 21%.

7. Percentage points vs percentage

Going from a 5% interest rate to a 7% rate is a 2 percentage point increase, but a 40% relative increase in the rate itself. The distinction matters in finance and statistics.

Skip the mental maths with our Percentage Calculator, which covers all three core percentage problems in one tool.