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Calculate a Percentage Decrease

Calculate percentages instantly for discounts, price increases, decreases, tax, tips, markups and everyday maths. PercentEazy is a free online percentage calculator with no sign-up required. Simply enter your numbers and get the answer.

How to Calculate a Percentage Decrease

A percentage decrease shows how much a number has fallen compared with its original value. It is useful for measuring reductions in prices, costs, sales, weight, energy use and many other everyday situations.

To calculate a percentage decrease, first subtract the new value from the original value. Divide the difference by the original value, then multiply the result by 100.

 

Formula

Percentage decrease = ((Original value − New value) ÷ Original value) × 100

 

Example 1: A Sale Price

A jacket originally costs £120 and is reduced to £90.

Difference = £120 − £90 = £30
£30 ÷ £120 = 0.25
0.25 × 100 = 25%

The price has decreased by 25%.

 

Example 2: Reducing a Monthly Bill

Suppose your electricity bill falls from £160 to £136.

Difference = £160 − £136 = £24
£24 ÷ £160 = 0.15
0.15 × 100 = 15%

Your electricity bill has decreased by 15%.

 

Example 3: Measuring a Reduction

A business reduces its monthly packaging use from 500 units to 425 units.

Difference = 500 − 425 = 75
75 ÷ 500 = 0.15
0.15 × 100 = 15%

Packaging use has therefore decreased by 15%.

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When Is Percentage Decrease Useful?

Percentage decrease is useful whenever you want to compare a lower new value with a higher original value. Common examples include calculating discounts, measuring reductions in household expenses, comparing falling prices, tracking reductions in business costs and measuring changes in quantities over time.

 

A Common Percentage Decrease Mistake

Always divide the decrease by the original value, not the new value.

For example, if a price falls from £100 to £80, the decrease is £20. Dividing £20 by the original £100 gives a 20% decrease. Dividing by £80 would give 25%, which does not correctly describe the decrease from the starting price.

 

Percentage Decrease vs Percentage Difference

These calculations answer different questions. Percentage decrease measures a change from an original value to a lower new value. Percentage difference compares two values without treating either one as the starting value.

If something falls from £100 to £80, you normally want percentage decrease. If you simply want to compare two measurements without treating either as the starting value, percentage difference may be more appropriate.

 

Frequently Asked Questions

Can a percentage decrease be more than 100%?

For ordinary positive quantities that cannot fall below zero, no. A fall from £100 to £0 is a 100% decrease.

 

Is a 20% decrease followed by a 20% increase back to the original value?

No. If £100 decreases by 20%, it becomes £80. Increasing £80 by 20% gives £96. It would need to increase by 25% to return from £80 to £100.

 

What if the new value is higher than the original value?

Then you have a percentage increase rather than a percentage decrease, so use the Percentage Increase Calculator.

 

Related Calculators

Percentage Increase Calculator — calculate how much a value has increased.

Percentage Change Calculator — measure the overall percentage change between an original and new value.

Percentage Difference Calculator — compare two values when neither is considered the starting value.

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