On This Page
- The drop in one line
- Three modes for three unknowns
- The loss-and-recovery table
- Checking a discount
- Drops in business numbers
- Percentage decrease in Excel
- How the calculator is verified
- FAQ
The Drop in One Line
A TV that was $850 and is now $595 has dropped $255, and $255 ÷ $850 = 30%. The size of a drop only means something next to its starting point: losing 50 is a 50% fall from 100 but only 5% from 1,000.
Three Modes for Three Unknowns
- Find % decrease: enter the old and new values. You also get the absolute change, the multiplier and the share of the original that is left. If the new value is higher, the label switches to "increase."
- Find new value: Original × (1 − % ÷ 100). A $240 coat at 35% off costs $240 × 0.65 = $156. The multiplier gets you there in one step.
- Find original value: New ÷ (1 − % ÷ 100). $156 after 35% off was $156 ÷ 0.65 = $240. A 100% drop is blocked here because it would mean dividing by zero.
The Loss-and-Recovery Table
A fall and a rise of the same percentage do not cancel. $100 up 25% is $125, and down 25% from there is $93.75. Because the recovery starts from a smaller base, getting back always takes a bigger percentage than the loss. The gain needed after an x% fall is x ÷ (100 − x) × 100:
| Fall | Gain needed to get back |
|---|---|
| 10% | 11.11% |
| 20% | 25% |
| 25% | 33.33% |
| 30% | 42.86% |
| 50% | 100% |
| 75% | 300% |
A portfolio falling from $24,500 to $19,110 is a 22% drawdown that needs a 28.2% gain to recover. A 12% pay cut takes $72,000 to $63,360, and restoring it needs a 13.64% raise. The Percentage Increase Calculator works the rise side. When the thing falling is itself a rate, such as interest going from 5% to 4%, you also need percentage points vs percent change: that is a 1-point drop but a 20% fall.
Checking a Discount
A $80 jacket at 40% off is $80 × 0.60 = $48. To audit a "Sale $63, was $90" label, the claimed cut is $27 ÷ $90 = 30%, and $63 ÷ 0.70 = $90 confirms it. If the reverse math gives a different "was" price, the advertised percentage is wrong. A $42 item after 40% off was originally $42 ÷ 0.60 = $70.
Stacked discounts shrink: 20% off and then another 10% is 0.80 × 0.90 = 0.72, a 28% total, not 30%.
Drops in Business Numbers
- Revenue: $1.2 million down to $960,000 is a 20% decline, a fifth of the business gone year on year.
- A price cut that sells more: cutting price 10% while selling 12% more units gives 0.90 × 1.12 = 1.008, revenue up 0.8%. The Profit Margin Calculator shows what the cut does to margin.
- A cost-reduction target: cutting $480,000 of spend by 15% means reaching $408,000, a $72,000 saving, which is easier to budget than the percentage alone.
If the direction of a change is unclear, the Percentage Calculator gives a signed result that tells you whether it rose or fell.
Percentage Decrease in Excel
With the old value in A2 and the new value in B2:
- Decrease as a positive number:
=(A2-B2)/A2, formatted as a percentage. - Signed change (negative means a fall, the usual reporting convention):
=(B2-A2)/A2 - Value after a % cut in C2:
=A2*(1-C2/100), or=A2*(1-C2)if C2 is formatted as a percentage. - Original before the cut:
=B2/(1-C2/100)
How the Calculator Is Verified
Find Decrease actually computes a signed percentage change, ((old minus new) divided by the absolute value of old) times 100, and if the new value turns out larger than the old one the result label switches itself to "Percentage increase" instead of forcing a negative decrease onto the display. Find Original Value divides the new value by (1 minus percent/100), the exact inverse of the multiplication Find New Value performs, and the code specifically blocks a 100% decrease input in that mode since dividing by zero would produce an undefined original value. Each of the three panels reads only the two fields it needs and recalculates on every keystroke, so nothing carries over from one mode to another when the dropdown changes.
Frequently Asked Questions
How do you calculate percentage decrease in salary?
Use current salary as "old" and new (lower) salary as "new." Old salary $75,000, new salary $67,500: ($75,000 − $67,500) ÷ $75,000 × 100 = $7,500 ÷ $75,000 × 100 = 10% decrease. To find a reduced salary from a known cut percentage: new salary = current × (1 − cut% ÷ 100).
Can percentage decrease be more than 100%?
Not for a standard value that starts positive and stays above zero. A 100% decrease means the value fell to exactly zero. If a value goes negative (for example a profit turning into a loss), the formula still works mathematically and can produce numbers above 100%, but in that context "percentage decrease" is less meaningful than "percentage change." For negative starting values, the sign convention can produce counterintuitive results.
How do you calculate percentage decrease in revenue or sales?
Use last period's revenue as "old" and this period's as "new." Revenue fell from $4.2M to $3.36M: ($4.2M − $3.36M) ÷ $4.2M × 100 = $0.84M ÷ $4.2M × 100 = 20% decline. Report it as "revenue decreased by 20% year-over-year." For context on how this flows through to margin, the Gross Profit Calculator shows the effect of revenue changes on gross profit when cost of goods stays fixed.
References
- Khan Academy: Percent Change Review: Worked examples covering percentage increase and decrease with step-by-step solutions and practice problems.
- Microsoft Support: Calculate Percentage Change in Excel: Official documentation on percentage change formulas in Excel, including both increase and decrease scenarios.
- U.S. Bureau of Labor Statistics: Computing Price Changes: How the BLS calculates percentage changes in prices, with the formula applied to real Consumer Price Index data.