Percent Decrease Calculator

Use this percent decrease calculator to easily calculate the result from a percentage decrease by any amount.

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  1. How to calculate percent decrease?
  2. Examples of calculating percent decrease

    How to calculate percent decrease?

Percent decrease calculations are needed when comparing time periods, estimating percent decline (yearly, monthly, daily etc.), or comparing a new state to an old state of things. An example would be a discounted price versus an original price, usually during sales and promotions, or when you are offered a percent off the regular price of a product or service. A less fortunate circumstance would be a pay cut or salary reduction situation.

    Percent decrease formula

The formula for calculating percent decrease used in our percentage decrease calculator is:

Percent decrease = 100 - new / old * 100

where new is the newer quantity or measure, and old is the older quantity or measure. Let us see some examples to see how that works.

In other cases, you know the starting, or original quantity, measure, or price, and you want to estimate what it would be if it were decreased by a given percentage. Then the formula is:

Decreased value = base - base * % decrease / 100

where base is the starting amount and % decrease is the percentage to reduce it by. Let us see some examples to see how it works.

    Examples of calculating percent decrease

A few practical examples should illuminate the use of percent reduction calculations in various settings and how to work out the math.

Example: new versus old price

Let us say you walk into a store and you see a 30% discount on an item due to a sale, promotion, or maybe you have a 30 percent off coupon you can use. Now, if you see that the original price is $100, how do you estimate the final price you need to pay? You use our calculator in the "decrease X by Y" mode, or you can calculate it manually by plugging the numbers into the second formula above to get $100 - $100 x 30 / 100 = $100 - $100 x 0.3 = $100 - $30 = $70 final price after decreasing it by the percent off.

If, however, you know the old price was $100 and the new price is $70, and you want to calculate the percent decrease, then you use the first formula: 100 - $70 / $100 * 100 = 100 - 0.7 * 100 = 100 - 70 = 30% decrease.

Decrease in expenses example

In this example use case of our percent reduction calculator, you run a company and you have attempted to limit your expenses in order to stay cash positive. In the previous year you incurred expenses of $500,000 during the same time period, while this year you only have $400,000 in outlays. What percent reduction have you achieved? To calculate the decline in expenses, divide the current expenses by the prior expenses: $400,000 / $500,000 = 0.8, then multiply by 100 to get 80, then subtract that from 100. The final result is that you have managed to decrease your expenses 20% year over year.

In another scenario your accountant has told you that you need to decrease your start-ups capital burn by 40% if you want to make it to the end of the year. Last month you spent $50,000, how much should you spend next month to meet the 40% target? Using the second formula, you calculate that you need to stay below $50,000 - $50,000 * 40 / 100 = $50,000 - $50,000 x 0.4 = $50,000 - $20,000 = $30,000 a month to stay afloat. In other words, decreasing your burn rate by 40% equals reducing it to $30,000 a month.

Calculate revenue or salary after taxes

You might want to calculate your after-tax salary (net salary), or after-tax revenue (net revenue), knowing your pre-tax yearly salary or revenue is $80,000 and that your total tax rate is 42%. You can, of course, use our percentage decrease calculator in the "X decreased by Y%" mode, or you can decrease $80,000 by 42% yourself like so: $80,000 - $80,000 * 42 / 100 = $80,000 - $80,000 x 0.42 = $80,000 - $33,600 = $46,400 net salary / net revenue. The example works out to a pay reduction of close to thirty-four thousand dollars.

Example: decrease in body mass (weight)

Your general practitioner has told you that you need to lose 5% of your weight in order to keep your body in a healthy condition and you want to know how many pounds (or kg) you need to lose. You currently weigh at 200 pounds, so you can just plug that into our percent decrease calculator, or by using the second formula calculate that you need to get to 200 - 200 * 5 / 100 = 200 - 10 = 190 pounds to be in good health.

Say you are trying to lose weight in order to get to your healthy weight range, and your average weight for a few weeks was 160 pounds. However, today the scale shows that you weigh only 150 pounds and you want to know what percentage increase it represents. Of course, it is easiest to use our online percentage decrease calculator, but if you want to do the math by hand, it is 100 - 150 / 160 * 100 = 100 - 0.9375 * 100 = 100 - 93.75 = 6.25 percent decrease in body weight.

Cite this calculator & page

If you'd like to cite this online calculator resource and information as provided on the page, you can use the following citation:
Georgiev G.Z., "Percentage Decrease Calculator", [online] Available at: URL [Accessed Date: 27 Jan, 2022].