Percentage Increase/Decrease Calculator
Increase or decrease a value by a given percentage and see the new amount.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Percentage Increase/Decrease Calculator
This calculator applies a percentage increase or decrease to any number. Enter your starting value, the percentage, and choose increase or decrease. The result updates live as you type.
- Enter your value. This is the number you want to adjust, such as a price, salary, measurement, or score.
- Enter the percentage. Type the percentage you want to increase or decrease by.
- Choose increase or decrease. Select whether you want to add or subtract the percentage from your value.
- Read the result. The new value and the change amount appear instantly. Use Copy or Share to save the result.
Increase formula: Value x (1 + Percent/100). Decrease formula: Value x (1 - Percent/100). The calculator handles decimals and large numbers.
About Percentage Increase and Decrease
Increasing or decreasing a number by a percentage is one of the most practical math operations. You encounter it when calculating sales tax, applying discounts, adjusting salaries, scaling recipes, and estimating growth. The operation multiplies the original value by a factor derived from the percentage, giving you the final result in one step.
A common mistake is adding the percentage directly to the number. For example, increasing 200 by 15% is not 200 + 15 = 215. It is 200 x 1.15 = 230. This calculator handles the math correctly every time.
Frequently Asked Questions
How do I increase a number by a percentage?
Multiply the number by (1 + percentage/100). For example, to increase 200 by 15%, calculate 200 x 1.15 = 230.
How do I decrease a number by a percentage?
Multiply the number by (1 - percentage/100). For example, to decrease 200 by 15%, calculate 200 x 0.85 = 170.
Can I decrease by more than 100%?
Yes, the calculator allows it. Decreasing by more than 100% will produce a negative result. For example, decreasing 200 by 150% gives 200 x (1 - 1.5) = 200 x (-0.5) = -100.