Calculators
Percentage Increase and Decrease Formula
Whether you're calculating a salary raise, working out how much a price has changed, or tracking growth in data — it's the same formula. Here's how to use it, with examples that show the working.
The formula
% Change = ((New − Old) ÷ Old) × 100
Positive result: increase. Negative result: decrease. The original (old) value is always in the denominator — a mistake people commonly make is putting the new value there instead.
Percentage increase examples
Salary raise: £32,000 → £35,200
((35,200 − 32,000) ÷ 32,000) × 100 = +10%
Website traffic: 4,200 → 5,880 visits
((5,880 − 4,200) ÷ 4,200) × 100 = +40%
Product price: £24.99 → £27.99
((27.99 − 24.99) ÷ 24.99) × 100 = +12%
Percentage decrease examples
Sale price: £120 → £84
((84 − 120) ÷ 120) × 100 = −30%
Store returns: 340 → 255 per month
((255 − 340) ÷ 340) × 100 = −25%
App size: 48 MB → 31.2 MB
((31.2 − 48) ÷ 48) × 100 = −35%
Applying a percentage increase directly
If you already know the percentage and want to apply it — rather than calculate what it is — multiply by the multiplier directly.
For an increase, multiply by (1 + rate). For a decrease, multiply by (1 − rate). This avoids the two-step process of calculating the change and then adding or subtracting it.
Calculate percentage change instantly
Type the starting and ending value. Get the increase or decrease, with the formula.
Use the calculator →Frequently asked questions
What is the formula for percentage increase?
Percentage increase = ((New Value − Original Value) ÷ Original Value) × 100. For example, if a price rises from £40 to £52: ((52 − 40) ÷ 40) × 100 = (12 ÷ 40) × 100 = 30%. A positive result always means an increase. The original value — not the new one — goes in the denominator.
What is the formula for percentage decrease?
The formula is identical: ((New Value − Original Value) ÷ Original Value) × 100. When the new value is lower, the numerator is negative, giving a negative result. If a price falls from £80 to £60: ((60 − 80) ÷ 80) × 100 = (−20 ÷ 80) × 100 = −25%. The decrease is 25%.
How do I calculate a 10% increase on a value?
Multiply the value by 1.10. A 10% increase on £340 is £340 × 1.10 = £374. For any percentage increase, multiply by (1 + percentage/100). A 7.5% increase on £200 is £200 × 1.075 = £215. This is faster than calculating the increase separately and adding it on.
How do I reverse a percentage increase?
Divide by (1 + rate). If a price after a 25% increase is £125, the original was £125 ÷ 1.25 = £100. A common mistake is to subtract 25% from £125 (which gives £93.75 — wrong). You must divide by the multiplier, not subtract the percentage from the new value.
What is a compound percentage increase?
A compound increase applies a percentage to the result of the previous period, not the original value. If £1,000 grows at 5% per year for 3 years: Year 1: £1,050. Year 2: £1,102.50. Year 3: £1,157.63. The formula is: Final = Original × (1 + rate)^n. Simple (non-compound) percentage increase would give £1,150 after 3 years.
What is the difference between absolute and relative change?
Absolute change is the raw difference: £52 − £40 = £12 increase. Relative change (percentage change) expresses that difference as a proportion of the original: (£12 ÷ £40) × 100 = 30%. A £100 increase from £200 to £300 is a 50% relative change. A £100 increase from £10,000 to £10,100 is only a 1% relative change — the absolute change is identical, the relative change is very different.