Percentage Calculator
Calculate percentages, percentage increases, decreases, and more with our easy-to-use calculator.
Calculation
Percentage Formulas
- X% of Y: (X/100) × Y
- X% Increase: Y + (Y × X/100)
- X% Decrease: Y - (Y × X/100)
- X is what % of Y: (X/Y) × 100
How the Percentage Calculator Works
The percentage calculator handles common percent questions: finding a percent of a number, increasing or decreasing a value, and finding what percent one value is of another.
Formula
X percent of Y = X / 100 x Y. Percentage change = (new value - old value) / old value x 100.
Example
If a $200 item is discounted by 15%, the discount is $30 and the new price is $170.
Limitations
Percent calculations are mathematical helpers. For finance, tax or scientific work, make sure the underlying numbers and rounding rules are appropriate.
How to use the result responsibly
- Check that every input uses the unit and time period shown beside the field.
- Compare the result with the worked example and formula above.
- For financial, tax, health, or legal decisions, confirm current rules with a qualified professional or the relevant authority.
Frequently Asked Questions
How do I calculate a percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100.
Why can percentages go over 100?
A percentage compares values. If the part is larger than the base, the result can be more than 100%.
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Editorially reviewed August 18, 2026. Read our calculation methodology and editorial policy.