Percentage Decrease Calculator

Q: How do I calculate percentage decrease?

Subtract the new value from the original, divide by the original, and multiply by 100. For $120 → $90: (120 − 90) ÷ 120 × 100 = 25%.

Q: What's the difference between percentage decrease and percentage difference?

Decrease divides by the starting value and has a direction (down). Percentage difference divides by the average of the two values and is symmetric — order doesn't matter. Use decrease for "it fell"; use difference for comparing two readings.

Q: If something drops 25%, how much does it need to rise to get back?

33.33%. A 25% fall on $120 leaves $90, and $90 needs $30 more — which is 33.33% of $90, not 25%. The two percentages are measured against different bases.

Q: How do I take 25% off a price?

Multiply by 0.75. $80 × 0.75 = $60, so you save $20. The calculator's discount mode shows both the sale price and the amount saved.

What are you working out?

Starting amount

Ending amount

Percentage decrease

25%

Difference: 30 lower than where you started
Worked as: (120 − 90) ÷ 120 × 100 = 25%

The formula divides by the starting amount, not the ending one — that's why a price going 120 → 90 is a 25% decrease, while 90 → 120 back is a 33% increase. Comparing a change in the other direction? Use the percentage increase calculator.

$120 falling to $90 is a 25% decrease — a drop of $30, measured against the $120 you started from. Flip to the discount mode and it works the other way: 25% off an $80 price is $60, saving $20. The direction is fixed on this page: if your second number is the larger one, the calculator reports an increase instead of quietly showing a negative decrease.

The one formula, and the one that isn't

Percentage decrease divides by the starting value — that's what makes it directional:

decrease % = (original − new) ÷ original × 100
difference = original − new

Worked example — the page default, 120 → 90:

Difference: 120 − 90 = 30
Divide by the original: 30 ÷ 120 = 0.25
× 100 = 25% decrease

A 25% decrease is not the same as a 25% increase in reverse. Once something has fallen 25%, it needs a 33.33% rise to get back to where it was: 90 × 1.3333 = 120. The fall was measured against 120; the climb is measured against 90. If you need the symmetric comparison — two readings with no "before" and "after" — use the percentage difference calculator, which divides by the average of the two.

Taking a percent off a price

The second mode answers the shopping question:

sale price = price × (1 − discount%)
saved      = price × discount%

25% off $80 = $80 × 0.75 = $60, saving $20. The stacking case trips people up: 50% off, then another 50% off is not free. $100 → $50 → $25, which is 75% off in total, because the second discount applies to the already-reduced price.

Where decreases get misread

From	To	Change	Decrease
$120	$90	−$30	25%
$250	$200	−$50	20%
$1,500	$1,200	−$300	20%
$80	$60	−$20	25%

Same percentage, different dollars — and the reverse direction is asymmetric: recovering from the 25% drop above needs +33.33%, while recovering from the 20% drop needs +25%. The bigger the fall, the bigger the climb back, and the gap widens fast: a 50% fall needs a 100% rise to break even.

Two edge cases are handled explicitly rather than printed as a number:

Original = 0: the percentage is undefined (dividing by zero), so the calculator says so instead of showing infinity.
New > original: that's an increase, and it's reported as one. Entering 90 → 120 gives −33.33% — the calculator flags it as an increase rather than showing a negative decrease, because that's what the numbers you typed actually describe.

How to use this calculator

Pick the mode — between two amounts for the percentage decrease, take a percent off for sale prices.
For the first mode, enter the original and the new amount ($120 and $90 are pre-filled).
For the discount mode, enter the price and the discount percent ($80 and 25% are pre-filled).
Read the percentage, the dollar difference, and the direction.
Open the discount chart to see what the usual percentages come to on your price.

Frequently asked questions

How do I calculate percentage decrease?

Subtract the new value from the original, divide by the original, and multiply by 100. For $120 → $90: (120 − 90) ÷ 120 × 100 = 25%.

What's the difference between percentage decrease and percentage difference?

Decrease divides by the starting value and has a direction (down). Percentage difference divides by the average of the two values and is symmetric — order doesn't matter. Use decrease for "it fell"; use difference for comparing two readings.

If something drops 25%, how much does it need to rise to get back?

33.33%. A 25% fall on $120 leaves $90, and $90 needs $30 more — which is 33.33% of $90, not 25%. The two percentages are measured against different bases.

How do I take 25% off a price?

Multiply by 0.75. $80 × 0.75 = $60, so you save $20. The calculator's discount mode shows both the sale price and the amount saved.

Is "50% off, then an extra 50% off" the same as 100% off?

No. The second discount applies to the reduced price: $100 → $50 → $25. That's 75% off in total, not free.

Why does it say the percentage isn't defined?

Because the original value is 0 — there's nothing to measure a decrease against. The calculator reports that instead of printing infinity, and the same rule applies when you enter 0 as the starting number.

Data sources: Both formulas are arithmetic definitions rather than published rates — percentage decrease divides by the original value, the standard definition used across this site's calculators — so every figure here can be reproduced by entering the same two numbers (the defaults are pre-filled: 120 → 90, and 25% off $80). The discount examples use round prices for illustration; real sale pricing may stack, exclude items, or apply after other credits. Related tools: percentage increase calculator, percentage difference calculator, percentage calculator, all math calculators.