How to Calculate Percentage Increase & Decrease

The formula

Percentage change = (new value – old value) ÷ old value × 100.

A positive result is an increase, a negative result is a decrease.

Rent goes from $1,200 to $1,320: (1,320 – 1,200) ÷ 1,200 × 100 = 10% increase.

Sales drop from 80 to 60: (60 – 80) ÷ 80 × 100 = -25%, a 25% decrease.

Or skip the maths: enter the two numbers in the Percentage Calculator's 'From… to…' box.

Dividing by the new value instead of the old one. Also, a 50% drop followed by a 50% rise does not get you back to where you started: 100 → 50 → 75.

If an interest rate moves from 4% to 5%, that's a rise of 1 percentage point – but a 25% increase in the rate itself.

How do I calculate a percentage of a number?

Multiply by the percentage and divide by 100: 15% of 80 = 12.

How do I reverse a percentage increase?

Divide by (1 + rate): $110 after a 10% rise was $100 before.

Is there a calculator?

Yes – the free Percentage Calculator does all three common calculations.