Percentage Decrease Calculator
Calculate percentage decrease from one value to another
Reliable calculator with instant results. Clean interface, accurate computations.
Formula
((original - new) / original) × 100How to Use Percentage Decrease Calculator
- Fill in the calculator with your numbers.
- Verify your inputs are correct.
- Read the instant calculation results.
- Copy or apply the results as needed.
Examples
Percentage decrease scales a number down, the arithmetic behind a discount, a pay cut, or a population decline, and its close relative, percentage increase, is what makes the classic trap possible: apply a decrease and then reverse it with the same percentage increase, and you land below the original number, not back on it.
The formula
new value = original x (1 - percent / 100)- original
- the starting value
- percent
- the rate of decrease
Worked example
An $85 jacket marked down 20% costs 85 x 0.80 = $68, a saving of $17. If the store later raises that $68 back up by 20%, the price becomes 68 x 1.20 = $81.60, still $3.40 short of the original $85, because the 20% increase is calculated on the smaller, discounted price rather than on the original one.
What trips people up
- Reversing a discount with the same percentage increase never gets back to the original price, since the increase is applied to a smaller base.
- Two discounts do not stack by addition. Taking 20% off and then another 10% off is a combined 28% off, not 30%, because the second discount applies to the already-reduced price.
- A percentage cannot decrease a value by more than 100%; beyond that the result goes negative, which is only meaningful for signed quantities like temperature or balance.
Frequently asked questions
- How do I find the original price before a known discount?
- Divide the discounted price by (1 - percent / 100); if $68 already reflects a 20% discount, the original price is 68 / 0.80 = $85.
- Do two discounts applied one after another add together?
- No. Successive discounts compound on a shrinking base, so 20% off followed by 10% off is a combined 28% off the original price, not a flat 30% off.
- What percentage decrease turns a value into zero?
- Exactly 100%. Anything less than 100% leaves a positive remainder, and a percentage decrease greater than 100% would only make sense for a signed quantity that can go negative.
- Is a 50% decrease the same as halving a value?
- Yes, those are identical, since new value = original x (1 - 0.5) = original x 0.5, which is exactly half.
- Why does reversing a price cut with the same percentage increase always fall short of the original?
- The increase that follows is calculated on the smaller, already-discounted price, so it adds back less in absolute terms than the discount removed.