How do you calculate a percentage decrease?

New value = original × (1 − percent/100). 100 decreased by 15% = 85. Savings = original − new value.

Is percent off the same as a percentage decrease?

Yes, when there is a single rate and it applies to the original price. The retail wording “30% off” means decrease by 30%. Stacked offs are several decreases, not one visit to this tool with the rates added.

What if the rate is above 100%?

The formula produces a negative result, which is not a price. A discount over 100% off is not a meaningful shelf tag. Check the input before you treat the output as money.

Is percent off the same formula?

Yes for a single rate applied to the original price. The discount calculator uses it and labels the outputs as pay and save. Stacked percent-off offers are several decreases. Add the rates only if the promotion literally says the percents combine that way, which most do not.

What remains after a 100% decrease?

Zero. There is no base left to increase back to the original. A forecast that says “down 100%” and also quotes a leftover is contradicting itself.

Can the starting value be negative?

The arithmetic will run. A negative base times a positive leftover is still negative, and “a decrease” in ordinary English may not match the sign you get. For money and counts, start from a positive amount and use direction to say whether it grows or shrinks.

How is this different from percentage change?

Here you bring the rate. Change discovers the rate from two observations. They confirm each other: decrease 200 by 10% to get 180, then ask for the change from 200 to 180 and see 10% down.

Percentage Decrease Calculator

Decrease a starting value by any percentage. Useful for discounts, reductions, depreciation estimates, and “minus X%” math.

Written and maintained by Ricardo Rodrigues · Last updated October 7, 2026 · What changed

Who this calculator is for

Use this when one rate comes off one starting value: a single markdown, a budget cut, a “down 15%,” a forecast that says the figure will be lower by a stated percent. You want both the remainder and the size of the cut. The page opens with Decrease selected so a sale-style question does not accidentally add.

A discount calculator is the same multiplication with the labels “you pay” and “you save.” Come here when the thing being reduced is not a shelf price — headcount, energy use, a grade threshold — or when you want the decrease formula stated as a decrease. For two promotions stacked on one price, do not add the rates; the stacked-discounts guide is the one that multiplies the leftovers.

Percentage Increase / Decrease

Increase or decrease a value by a percentage

Starting value

By percentage

Direction

Quick select

Result

Enter values to calculate

Comparison table

A rise and a fall of the same percent do not cancel
Change	100 after rise	Then fall by same %	Net change	Fall needed to undo rise
10%	110	99	-1%	9.09%
20%	120	96	-4%	16.67%
25%	125	93.75	-6.25%	20%
50%	150	75	-25%	33.33%
75%	175	43.75	-56.25%	42.86%

About this percentage decrease

A decrease multiplies by what remains: value × (1 − rate/100). Thirty percent off is not a mysterious retail formula; it is this one. You pay 70% of the price. The amount you save is the other 30%, and the two pieces add back to the original.

Use it for a single cut — a markdown, a budget reduction, a “down by.” Do not type the sum of two successive discounts. Twenty percent off and then ten percent off is a multiply of 0.80 and 0.90, a 28% decrease, not a 30% decrease.

How to use each field

Starting value: The amount before the cut. The rate applies to this number, not to the number you hope to land on. A €200 jacket, a 50-person team, a 1,000-unit forecast: whatever is about to be reduced.
By percentage: The rate removed. 10 means multiply by 0.90. 100 means multiply by zero. Above 100 the formula produces a negative result, which is arithmetic, not a price. Quick-select can overwrite a rate you typed.
Direction: This URL starts on Decrease. Increase is one tap away and will add the piece instead. If the result is larger than the start, look at the direction button before you blame the rate.
Result and the amount removed: The large number is what remains. The secondary amount is the cut. 200 decreased by 10% remains 180, and the cut is 20. Those two add back to 200. If you are talking about savings, quote the cut. If you are talking about what is left, quote the remainder.

When to use this calculator

One rate will be removed from one starting value, and you want both the remainder and the size of the cut.
You are checking a sale tag that states a single percent off.
You need to see how large a cut must be before it crosses a cost or a floor you care about.

Worked examples

Example calculations for Percentage Decrease
Question	Answer
100 decreased by 15%	85
200 decreased by 10%	180
80 decreased by 25%	60

Walkthroughs

A team reduced by 15%

Forty people, down 15%. Starting value 40, by percentage 15, direction Decrease. The cut is 6 people and 34 remain. You cannot employ 0.4 of a person if a later rate does not divide evenly; say so. 12% of 40 is 4.8, which is a planning figure, not a name on a list. The calculator reports the product. Rounding people is a management decision.

If leadership instead says “we need to be at 34, what percent is that?”, you do not have a rate yet. Change from 40 to 34 is a 15% decrease. The match is how you confirm the announcement. This page is the direction that starts from the rate.

Depreciation used as a teaching decrease, not as tax law

A textbook says a machine worth 8,000 loses 20% of its current value each year, for two years. Year one: 8,000 decreased by 20% = 6,400. Year two starts at 6,400, not at 8,000: 6,400 × 0.80 = 5,120. The two-year loss is 2,880, which is 36% of the original, not 40%. Straight-line depreciation in a tax code is often a different rule entirely. This walkthrough is only the successive-percent version a textbook asked for.

Formula

Goal	Formula
Value after decrease	value × (1 − percent/100)

Remaining = start × (1 − rate/100). Cut = start × (rate/100). They sum to the start. 200 × 0.90 = 180, and 200 × 0.10 = 20. You can also subtract the cut from the start. Both paths are one decrease. Neither path stacks a second offer.

The undo is not the same percent. From 180, an increase of 10% is 198, short of 200 by 2. The return trip divides by 0.90, which is an increase of about 11.11%. Any time someone says “we’ll add back the same percent later,” run both directions before you agree.

Two decreases in a row multiply. A 20% cut and then a 10% cut is 0.80 × 0.90 = 0.72, so 28% off the original, not 30%. Half off and then half off again leaves a quarter, which is 75% off, not 100% off. This page will do the second cut if you type the remainder as a new starting value. It will not add the badges for you, which is the correct refusal.

Mistakes this page will not catch for you

Undoing the decrease with the same percent

Cut 200 by 10% and you land on 180. Raising 180 by 10% lands on 198, not 200. Recovery needs about an 11.11% increase because the base shrank. This tool applies a rate; it does not find the return trip.

A 100% decrease

The result is zero. You cannot divide your way back to the original from zero. If a forecast claims “down 100%” and also quotes a remaining amount, one of those claims is wrong.

Reading a lower price as this formula when the rate was on a different base

A phone that “was 1,000, now 700” is a change from 1,000 to 700, a 30% decrease. You may type 1000 and 30 here and land on 700. If the tag does not state the percent, do not invent one and then congratulate the formula. Measure the change first.

FAQ

How do you calculate a percentage decrease?: New value = original × (1 − percent/100). 100 decreased by 15% = 85. Savings = original − new value.
Is percent off the same as a percentage decrease?: Yes, when there is a single rate and it applies to the original price. The retail wording “30% off” means decrease by 30%. Stacked offs are several decreases, not one visit to this tool with the rates added.
What if the rate is above 100%?: The formula produces a negative result, which is not a price. A discount over 100% off is not a meaningful shelf tag. Check the input before you treat the output as money.
Is percent off the same formula?: Yes for a single rate applied to the original price. The discount calculator uses it and labels the outputs as pay and save. Stacked percent-off offers are several decreases. Add the rates only if the promotion literally says the percents combine that way, which most do not.
What remains after a 100% decrease?: Zero. There is no base left to increase back to the original. A forecast that says “down 100%” and also quotes a leftover is contradicting itself.
Can the starting value be negative?: The arithmetic will run. A negative base times a positive leftover is still negative, and “a decrease” in ordinary English may not match the sign you get. For money and counts, start from a positive amount and use direction to say whether it grows or shrinks.
How is this different from percentage change?: Here you bring the rate. Change discovers the rate from two observations. They confirm each other: decrease 200 by 10% to get 180, then ask for the change from 200 to 180 and see 10% down.