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Percentage Decrease Calculator
Sign up to favourite this calculatorEnter where a value started and where it ended. The percentage decrease, the amount lost and the share of the original left appear as you type.
Percentage decrease
Difference
−160Starting value
750Final value
590Share of the original
78.67%Direction
DecreaseSave to My calculations
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Keep this calculation as a scenario, change any input above, and the Now column shows how the result moves. Keep up to three, A to C; Open puts one back in the calculator.
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Assumptions and limits
- An estimate from the numbers you entered, for guidance only. It is not financial, tax or medical advice.
- Calculator version 1, last updated 25 October 2026.
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How to use this calculator
- Enter the starting value — the figure the fall is measured from.
- Enter the final value, in the same unit.
- Read the percentage decrease above the supporting figures, and check the calculation line under the inputs, which shows the sum with your own numbers in it.
The share of the original is the figure to keep for discounts. A 30% decrease leaves 70% to pay, so any other price can be discounted by the same proportion by multiplying by 0.7.
What do I need to enter?
- Starting value — the figure the fall is measured from, any number from −1,000,000,000,000 to 1,000,000,000,000. It is the baseline the change is divided by.
- Final value — where the figure ended up, within the same range and in the same unit.
What do the results show?
- Percentage decrease — the main figure, rounded to two decimal places. If the final value is higher, the label says it is an increase instead.
- Difference — final minus starting value, with a + or − sign.
- Share of the original — the final value as a percentage of the starting value.
- Starting value, Final value andDirection — your inputs, and whether the value fell, rose or stayed the same.
- Calculation — the sum with your numbers in it. A starting value of zero shows "Not defined".
How to calculate a percentage decrease
A percentage decrease is the amount a value lost, expressed as a share of what it started at. The starting value is always the baseline — swapping the two numbers changes the answer.
Decrease = (Starting − Final) ÷ |Starting| × 100
- Starting — the value before the change, e.g. 750
- Final — the value after the change, e.g. 590
- Decrease — the fall as a percentage, e.g. 21.33%
Working through the example: 750 − 590 = 160, then160 ÷ 750 = 0.213333, and 0.213333 × 100 = 21.33%.
The bars around the starting value mean its size is used, ignoring any minus sign, so a fall from −100 to −200 reads as a 100% decrease rather than a rise.
If your value rose rather than fell, the Percentage Increase Calculator frames the same sum the other way round.
Worked examples
| Change | Difference | Decrease |
|---|---|---|
| 750 → 590 | −160 | 21.33% |
| 100 → 10 | −90 | 90% |
| 5,000 → 1,000 | −4,000 | 80% |
| 1,000 → 950 | −50 | 5% |
| 80 → 60 | −20 | 25% |
The middle rows show how far a percentage can be from the raw amount: a 90 fall on 100 and a 4,000 fall on 5,000 look nothing alike, but one is a 90% loss and the other 80%.
Frequently asked questions
How do I calculate percentage decrease?
Subtract the final value from the starting value, divide by the starting value, then multiply by 100. Going from 750 to 590 is a fall of 160, and 160 ÷ 750 × 100 gives a 21.33% decrease.
How do I take a percentage off a price?
Multiply by 1 minus the percentage as a decimal. Taking 25% off 80 means 80 × 0.75 = 60. Working the other way, if a price fell from 80 to 60 you can enter both values here and get the 25% back.
Why is a 25% fall not undone by a 25% rise?
Because the second percentage is taken from a different number. Take 25% off 80 and you have 60; add 25% back to 60 and you have 75, not 80. Reversing a 25% fall needs a 33.33% rise, since the base has shrunk.
Can a percentage decrease be more than 100%?
Only if the value falls past zero. A drop from 200 to −50 is a 125% decrease, which is why it usually signals a value that has gone negative rather than simply shrunk. A fall to exactly zero is always 100%.
What does the share of the original mean?
It is what is left, as a percentage. A 21.33% decrease leaves 78.67% of the original value standing, and the two always add up to 100%. It is the figure to use when a discount is described as "pay 80% of list price".
What if the final value is larger than the starting value?
Then it has gone up, and the calculator says so above the figure rather than reporting a negative decrease. The percentage increase calculator frames the same sum the other way round.
Last updated 25 October 2026.