Percentage Decrease Calculator
Find the percentage decrease from an original value to a new value, with the formula worked out using your numbers. Reverse it to decrease a number by a percent or recover the original price. Runs privately in your browser.
Percentage decrease is how much a value has fallen, expressed as a percent of its original value. You find it by dividing the amount of the decrease by the original amount and multiplying by 100, so a price that drops from $80 to $60 has a 25% decrease. A negative result means the value actually increased (Khan Academy: percentage increase or decrease).
How Percentage Decrease Calculator Works
Pick a mode and enter two numbers. Find % decrease takes the original and new value and shows the percent drop, the absolute change and the formula filled in with your numbers. Find new value decreases a number by a percent (for example, 250 minus 12%). Find original value works backwards from a sale price and the discount. Everything is calculated in your browser — no data is sent to any server.
How to Calculate Percentage Decrease
Percentage decrease measures how much a value has fallen relative to its original amount. The formula subtracts the new value from the original, divides by the original, and multiplies by 100. A positive result confirms a decrease; if the new value is actually higher, the result indicates an increase instead.
Percentage Decrease Formula
Percentage Decrease = ((Original Value − New Value) / Original Value) × 100
New Value = Original Value × (1 − Percentage Decrease / 100)
Where:
- Original Value = The starting number (before the decrease)
- New Value = The ending number (after the decrease)
Example Calculations
Example 1: Price Drop
Original price: $80 → Sale price: $64
- Decrease = ($80 − $64) / $80 × 100 = 20% decrease
Example 2: Stock Market Loss
Bought at: $150 → Current: $127.50
- Decrease = ($150 − $127.50) / $150 × 100 = 15% decrease
Example 3: Weight Loss
Starting weight: 200 lbs → Current weight: 185 lbs
- Decrease = (200 − 185) / 200 × 100 = 7.5% decrease
Percentage Decrease Formula: Worked Examples
To work out a percentage decrease by hand, follow three steps:
- Subtract the new value from the original value to get the decrease.
- Divide the decrease by the original value (always the starting number, never the new one).
- Multiply by 100 to turn the decimal into a percent.
The table applies the formula to common uses — price discounts, weight loss and sales decline:
| Use | Original | New | Working | % decrease |
|---|---|---|---|---|
| Price discount | $80 | $60 | (80 − 60) ÷ 80 × 100 | 25% |
| Monthly sales decline | 1,250 units | 1,000 units | (1,250 − 1,000) ÷ 1,250 × 100 | 20% |
| Weight loss | 200 lb | 185 lb | (200 − 185) ÷ 200 × 100 | 7.5% |
| Percent decrease from 50 to 40 | 50 | 40 | (50 − 40) ÷ 50 × 100 | 20% |
Going the other way, a 25% decrease of $80 is $80 × 0.75 = $60, and a $60 sale price after 25% off came from $60 ÷ 0.75 = $80.
Percentage Decrease vs Percentage Point Decrease
When the numbers are already percentages (interest rates, unemployment, test scores, market share), a drop can be described two ways. A percentage point decrease is the simple difference between the two percentages. A percentage decrease is that difference divided by the starting percentage. Mixing them up can make a change look five or ten times bigger or smaller than it is.
| Change | Percentage point decrease | Percentage decrease |
|---|---|---|
| Interest rate 5% → 4% | 1 point | 20% |
| Unemployment 10% → 8% | 2 points | 20% |
| Market share 40% → 30% | 10 points | 25% |
Why a 50% Drop Needs a 100% Rise to Recover
A percentage decrease and the increase needed to undo it are not the same size, because the recovery is measured from the smaller, lower value. If $100 falls 50% to $50, it must double (a 100% increase) to get back to $100. The required rise is d ÷ (1 − d), where d is the decrease as a decimal.
| Decrease | $100 becomes | Increase needed to recover |
|---|---|---|
| 10% | $90 | 11.11% |
| 20% | $80 | 25% |
| 25% | $75 | 33.33% |
| 50% | $50 | 100% |
| 75% | $25 | 300% |
Percentage Decrease vs Discount
A discount and a percentage decrease are mathematically the same thing. A "20% off" sale means the price decreased by 20% from the original. This calculator works for both — enter the original price and sale price to find the discount percentage, or enter the original price and discount percentage to find the sale price.
Why Percentage Decrease Is Not the Inverse of Percentage Increase
A common mistake: if something increases by 25% and then decreases by 25%, you do NOT end up where you started. Starting at 100, a 25% increase gives 125. Then a 25% decrease of 125 gives 93.75 — not 100. This asymmetry is important in finance, investment, and pricing calculations.
Last updated: October 2026
Frequently Asked Questions
How do I calculate percentage decrease?
Subtract the new value from the original value, divide by the original, and multiply by 100. Example: (80 - 64) / 80 × 100 = 20% decrease.
Is percentage decrease the same as a discount?
Yes. A "20% off" discount is exactly the same as a 20% decrease from the original price.
Why doesn't a 25% increase followed by a 25% decrease return to the original?
Because percentage changes are relative to the current value. 100 + 25% = 125. Then 125 - 25% = 93.75. The second calculation uses 125 as the base, not 100.
What is the difference between percentage decrease and percentage point decrease?
A percentage point decrease is the simple difference between two percentages, while a percentage decrease divides that difference by the starting percentage. An interest rate falling from 5% to 4% is a 1 percentage point decrease but a 20% decrease.
What is the percent decrease from 50 to 40?
It is a 20% decrease. Subtract 40 from 50 to get 10, divide 10 by the original value 50 to get 0.2, then multiply by 100 to get 20%.
Can I find the original price before a discount?
Yes. Switch to "Find original value" mode, enter the sale price and discount percentage, and the calculator computes the original pre-discount price.
Is Percentage Decrease Calculator free to use?
Yes, Percentage Decrease Calculator is completely free with no sign-up, no login, and no hidden fees. The tool runs entirely in your browser — your data never leaves your device.