How Do You Calculate Percentage Decrease?
To calculate percentage decrease, subtract the new value from the old value, divide the difference by the old value, and multiply by 100. The formula is ((Old Value − New Value) ÷ Old Value) × 100. For example, a jacket marked down from $120 to $90 is (120 − 90) ÷ 120 × 100 = 25% off.
Same Logic as Increase, Flipped Around
If you've read our guide on percentage increase, this will feel familiar — it's the mirror image. Instead of measuring how much something grew, you're measuring how much it shrank. Sales, discounts, price drops, weight loss, budget cuts: it's all the same math.
Percentage Decrease = ((Old Value − New Value) ÷ Old Value) × 100
Three steps, same as before:
- Find the difference. Subtract the new (smaller) value from the old (original) value.
- Divide by the old value. Again — the *original* number goes on the bottom. Always.
- Multiply by 100 to get the percentage.
Worked Example 1: A Sale Discount
A jacket was $120, now it's $90. What's the discount percentage?
Step 1: 120 − 90 = 30. You're saving $30.
Step 2: 30 ÷ 120 = 0.25.
Step 3: 0.25 × 100 = 25%.
That's a 25% discount. Worth it? Depends on the jacket, but at least the math is clear.
Worked Example 2: Stock Price Drop
You bought a stock at $64. It's now trading at $48. How much have you lost, percentage-wise?
Step 1: 64 − 48 = 16.
Step 2: 16 ÷ 64 = 0.25.
Step 3: 0.25 × 100 = 25%.
Down 25%. Ouch. (Here's a sobering follow-up: to get back to $64 from $48, the stock needs to rise 33.3%, not 25%. Decreases and increases aren't symmetric — more on that below.)
Worked Example 3: Weight Loss
You weighed 210 lb at the start of the year and now weigh 178 lb. What's the percentage decrease?
Step 1: 210 − 178 = 32. You lost 32 pounds.
Step 2: 32 ÷ 210 = 0.1524.
Step 3: 0.1524 × 100 = 15.24%.
About a 15% reduction in body weight. For context, doctors often cite 5–10% weight loss as the threshold for meaningful health improvements — so 15% is genuinely significant. Well done.
Worked Example 4: Subscription Price Cut
A software subscription dropped from $49/month to $35/month after you complained (politely) to support.
Step 1: 49 − 35 = 14.
Step 2: 14 ÷ 49 = 0.2857.
Step 3: 0.2857 × 100 = 28.57%.
Roughly a 29% saving. That's $168 a year back in your pocket — worth the five-minute chat.
Worked Example 5: Home Value Dip
A house appraised at $420,000 last year is now valued at $378,000.
Step 1: 420,000 − 378,000 = 42,000.
Step 2: 42,000 ÷ 420,000 = 0.10.
Step 3: 0.10 × 100 = 10%.
A 10% dip. Uncomfortable if you're selling, irrelevant if you're staying put for a decade.
The Asymmetry Trap (Important!)
Here's something that surprises people: a 25% decrease followed by a 25% increase doesn't get you back to where you started.
Take $100. Drop it 25%: $100 × 0.75 = $75. Now increase $75 by 25%: $75 × 1.25 = $93.75. You're still $6.25 short.
Why? Because the second percentage applies to a *smaller base*. To recover from a 25% loss, you need a 33.3% gain (25 ÷ 75 × 100). To recover from a 50% loss, you need a 100% gain — a double.
This matters enormously for investing. A portfolio that drops 50% needs to *double* just to break even. That's why downside protection matters more than most beginners think. The math is unforgiving on the way down.
Common Mistakes
Dividing by the New Value
Same trap as with increases. In Example 1, dividing 30 by 90 (the sale price) gives 33.3% — wrong. The discount is measured against the *original* price of $120. Always divide by where you started.
Reading "25% Off" as "Pay 25%"
A classic. "25% off" means you *save* 25% and *pay* 75%. If a $80 item is 25% off, you pay $80 × 0.75 = $60. Don't walk up to the register expecting to pay $20.
Stacking Discounts Incorrectly
"Extra 20% off already-reduced prices!" doesn't mean 40% off total. If a $100 item is 20% off ($80), and you get another 20% off the sale price, that's $80 × 0.80 = $64. Total discount: 36%, not 40%. Each discount applies to the already-reduced price. Retailers know this; now you do too.
Confusing "Decreased By" with "Decreased To"
"Prices decreased by 30%" means the new price is 70% of the old. "Prices decreased to 30%" means the new price is 30% of the old — a 70% drop. That little word changes everything. Read carefully.
Quick Discount Shortcuts
For common sale percentages, memorize the "pay" multiplier:
- 10% off → pay 0.90 × price
- 20% off → pay 0.80 × price
- 25% off → pay 0.75 × price
- 30% off → pay 0.70 × price
- 50% off → pay 0.50 × price (half — the easy one)
So a $65 shirt at 30% off: $65 × 0.70 = $45.50. You can do that in your head while standing in the store, which is exactly when it matters.
Frequently Asked Questions
What's the difference between percentage decrease and discount?
They're the same calculation. "Discount" is just the retail word for percentage decrease applied to prices. A 25% discount means the price decreased by 25% from the original. Same formula, same math.
Can percentage decrease be more than 100%?
In pure math terms, no — you can't decrease something by more than 100% without going negative (which doesn't make sense for prices, weights, or most real quantities). If someone claims a "120% price drop," they're either confused or selling something. The maximum real decrease is 100% (free).
How do I calculate the original price from a sale price and discount percent?
Rearrange the formula: Original = Sale Price ÷ (1 − Discount as decimal). Example: you paid $60 for a jacket at 25% off. Original = 60 ÷ (1 − 0.25) = 60 ÷ 0.75 = $80. Useful for checking whether that "was $80" tag is honest.
How do I do this in Excel or Google Sheets?
=(A1-B1)/A1 where A1 is the original value and B1 is the new value. Format the cell as a percentage. For the jacket example: =(120-90)/120 gives 25%.
Why do stores show "was/now" pricing instead of the percentage?
Because the raw numbers feel more concrete, and honestly, many shoppers won't do the math. But now you will. When you see "was $120, now $90," you know instantly: 25% off. If the discount were only 10%, the "was/now" framing might make it look bigger than it is. The percentage keeps everyone honest — including you, when you're deciding whether it's actually a deal.
Related tools
You can also use Explore all free online tools and Read more helpful articles as part of your workflow.
Using a how to calculate percentage decrease can make this task easier and more efficient when you need a simple online solution.
A how to calculate percentage decrease is especially useful when you want a quick browser-based workflow.