Percentage Decrease Calculator
Enter the original and the new, lower value to get the percentage decrease, with the working shown.
The calculator never sends or saves what you type.
Tracking weight? The weight loss percentage calculator takes lb or kg with no currency symbol, and a goal weight.
Need to take a percentage off a number instead? That formula and table are below.
The percentage decrease formula
Decrease % = (Original − New) ÷ Original × 100
A figure falls from 60 to 45.
- Fall = 60 − 45 = 15
- 15 ÷ 60 = 0.25
- 0.25 × 100 = 25% decrease
- Check: 60 − 25% = 45 ✓
Divide by the original, always. The same 15 measured against the new value (15 ÷ 45) is 33.3%, which is the percentage increase from 45 back up to 60 — a different question, and the reason a fall and the rise that undoes it never share a number. If your two values give a rise, the calculator says so rather than reporting a negative decrease; the percentage change calculator covers both directions in one place.
How to take a percentage off a number
The other direction: you know the original and the rate, and want the reduced value. Multiply by 1 minus the rate as a decimal — 20% off leaves 80% of the original, so × 0.8. For prices, the discount calculator does this and shows the saving.
New = Original × (1 − rate ÷ 100)
A 3,200 MB data allowance is cut by 10%.
- 1 − 10 ÷ 100 = 0.9
- 3,200 × 0.9 = 2,880 MB
- The cut itself: 3,200 − 2,880 = 320 MB
| Decrease by | Multiply by | 100 becomes |
|---|---|---|
| 5% | × 0.95 | 95 |
| 10% | × 0.9 | 90 |
| 12.5% | × 0.875 | 87.5 |
| 15% | × 0.85 | 85 |
| 20% | × 0.8 | 80 |
| 25% | × 0.75 | 75 |
| 30% | × 0.7 | 70 |
| 40% | × 0.6 | 60 |
| 50% | × 0.5 | 50 |
| 75% | × 0.25 | 25 |
Two cuts in a row multiply, they do not add: 10% off then 10% off is × 0.9 × 0.9 = × 0.81, a 19% decrease, not 20%.
Price cuts, weight and depreciation
A price cut. $150 to $120 is 30 ÷ 150 × 100 = a 20% decrease. Retailers say "20% off"; the calculation is the same. Be suspicious of a "was" price that never actually sold — the percentage is only as honest as the original it is measured from.
Weight. 92 kg to 85 kg is a 7.6% decrease. Progress quoted as a percentage flatters small changes on small bases and understates large ones on large bases; the kilograms are the number that matters, the percentage just makes two people comparable. Weight loss percentage, with 5% and 10% goal weights has its own calculator.
Depreciation. A car bought for $28,000 and worth $19,600 a year later has lost 30%. Year-on-year the rate is applied to each year's value, so three years at 30% leaves 0.7³ = 34% of the price, not 10%.
Latency. A p95 of 420 ms that comes down to 310 ms is 110 ÷ 420 × 100 ≈ 26.2%, a fall of just over a quarter. Say which percentile the figure is: the p99 rarely falls by the same share. For the Prometheus query behind a dashboard panel, OpsCanopy’s PromQL explainer breaks it down into plain English.
Below zero. A profit of $4,000 that becomes a loss of $1,000 has fallen by 125% — more than 100% is possible when the quantity can go negative. The calculator shows the figure and notes the sign.
Working backwards
Know the reduced value and the percentage, and want what it was beforehand? Divide by 1 minus the rate — adding the percentage back on gives the wrong answer, because it was taken off a larger number. The reverse percentage calculator does that division and shows why.
Tracking weight loss?
Weight loss as a percentage is the same arithmetic — starting weight minus current weight, divided by the starting weight — but a body weight has no currency, and most people want a goal weight too. The weight loss percentage calculator takes lb, kg or stone with no symbol, prints your 5% and 10% milestones and how far a goal weight is. Try 220 → 198 lb: a 10% loss.
Frequently asked questions
How do you calculate percentage decrease?
Take the original value minus the new value, divide by the original value, then multiply by 100. From 60 to 45: 60 − 45 = 15, then 15 ÷ 60 = 0.25, then × 100 = a 25% decrease. Divide by the original — the number you started from — never by the new one.
What is the percentage decrease from 60 to 45?
25%. The fall is 15, and 15 is a quarter of the original 60. Going back up from 45 to 60 is a 33.3% increase — the same 15 measured against the smaller number.
How do I take 15% off a number?
Multiply by 0.85. Taking 15% off leaves 85% of the original, and 85% is 0.85. So 240 less 15% is 240 × 0.85 = 204. For prices, the discount calculator on this site does that and shows what you save.
Is a percentage decrease the same as percent off?
Same arithmetic, different starting point. "Percent off" is the rate you apply to get the new price; "percentage decrease" is the rate you calculate from two prices you already have. A shirt marked 30% off has had a 30% decrease from its full price — the calculator above tells you that from the two prices, the discount calculator tells you the price from the rate.
Can a percentage decrease be more than 100%?
Not for a quantity that stops at zero. A 100% decrease takes a value to nothing; there is no lower to go by decreasing. Values that can go negative — a bank balance, a temperature, a profit — can fall by more than 100%, and the calculator will show the result with a note about the negative figure.
Why is a 25% decrease not undone by a 25% increase?
Because the increase is taken from the smaller number. 60 down 25% is 45; 45 up 25% is 56.25, not 60. To get back to 60 from 45 you need a 33.3% increase. The two rates are always different unless both are zero.
What is the difference between percentage decrease and percentage change?
Percentage change is the general measure and carries a sign; a percentage decrease is a change that happens to be negative, quoted as a positive number with the word "decrease". If your two numbers give a rise, the calculator above says so rather than reporting a negative decrease.