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.
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.