Percentage Decrease Calculator
Use this percentage decrease calculator to work out the percentage drop between a starting value and a final value, or to reduce a number by a chosen percentage. Enter your figures and the percentage decrease, the amount of the decrease and the full working are shown instantly — handy for price reductions, falls in sales or revenue, cost savings and depreciation, with all results in pounds sterling.
The percentage decrease formula
Percentage Decrease = ((Original Value − New Value) ÷ Original Value) × 100
- Subtract the new value from the original value to find the amount of the decrease.
- Divide that decrease by the original value so it is measured against the starting point, not the new value.
- Multiply by 100 to turn that fraction into a percentage. The result is always positive for a fall.
How to use this calculator
- Pick “Between two values” to compare a starting and final value, or “Decrease by a %” to take a percentage off a number.
- Enter your values — for example, costs falling from £250 to £210.
- The percentage decrease and the amount of the decrease appear instantly.
Worked examples
Price reduction
A product drops from £45 to £36 in a sale. Decrease = 45 − 36 = 9. Percentage decrease = 9 ÷ 45 × 100 = 20%. The price was cut by 20%.
Fall in sales or revenue
Monthly revenue falls from £18,000 to £15,300. Decrease = 18,000 − 15,300 = 2,700. Percentage decrease = 2,700 ÷ 18,000 × 100 = 15%. Sales were down 15%.
Decrease in costs
A supplier bill falls from £250 to £210. Decrease = 250 − 210 = 40. Percentage decrease = 40 ÷ 250 × 100 = 16%. Costs fell by 16%.
Reducing a number by a percentage
Reduce £250 by 16%. New value = £250 × (1 − 16 ÷ 100) = £250 × 0.84 = £210. The amount taken off is £40.
A decrease over 100%
A stock level falls from 400 to 120 units. Decrease = 400 − 120 = 280. Percentage decrease = 280 ÷ 400 × 100 = 70%. The stock dropped by more than half.
Percentage decrease, percentage change, percentage difference and discount
These terms are easy to mix up. Here is the difference, in plain English.
- Percentage decrease
- How much a value has gone down, expressed as a percentage of the original. Use it when you have a clear starting value and a lower new value.
- Percentage change
- A single figure that covers both increases and decreases — a positive result is an increase, a negative result is a decrease. Use the percentage change calculator when the direction is not known in advance.
- Percentage difference
- Compares two values without treating either as the starting point. It uses the average of the two as the base, so it is useful when neither number is clearly the original.
- Discount percentage
- The same maths as a percentage decrease, but applied to a price. A 20% discount is a 20% decrease in price — use the discount calculator for sale prices in pounds and pence.