Percent Calculator
Work out a percent of a number, find what percent one value is of another, or calculate a percentage increase or decrease, with clear steps.
15% of 200 is 30.
- Convert the percent to a decimal: 15 / 100 = 0.15.
- Multiply by the value: 0.15 × 200 = 30.
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All calculations run locally in your browser. Your entered values are not sent to an external service.
How to Use the Percent Calculator
Choose a mode, enter the two values, and select Calculate. The tool shows the result and the steps used to reach it.
- % of a number: enter the percent and the value to find that percent of the value.
- X is what % of Y: enter a part and a total to find the part as a percentage of the total.
- % change: enter an original value and a new value to find the percentage increase or decrease.
Switching modes updates the input labels so it is always clear which number goes where. Values can be decimals or negative, though a total of zero has no defined percentage and a starting value of zero has no defined percent change. To convert 0.75 to 75% or 15% to 0.15, use the Decimal to Percent Calculator. A store’s cost-to-selling markup belongs on the Markup Calculator. A sale markdown belongs on the Discount Calculator.
The Three Core Percent Formulas
A percent is a fraction out of one hundred. Converting the percent to a decimal and multiplying by the value gives the amount. For 15% of 200, compute 0.15 × 200 = 30.
To describe one number as a percentage of another, divide the part by the total and multiply by 100. For 30 out of 200, compute (30 / 200) × 100 = 15%.
Percent change compares a new value with an original value relative to the original. A positive result is an increase and a negative result is a decrease.
Percent Calculator Examples
Percent of a number
20% of 90 is 0.20 × 90 = 18. A tip of 18% on a $50 bill is 0.18 × 50 = $9.
What percent is one value of another
45 out of 60 is (45 / 60) × 100 = 75%. A score of 18 out of 20 is (18 / 20) × 100 = 90%.
Percentage increase
A price rising from 80 to 96 is ((96 − 80) / 80) × 100 = 20%.
Percentage decrease
A price dropping from 150 to 120 is ((120 − 150) / 150) × 100 = −20%, a 20% decrease.
Percentage Points vs Percent Change
A change from 40% to 50% is a rise of 10 percentage points, but relative to the original 40% it is a 25% increase because (50 − 40) / 40 × 100 = 25%. Percentage points describe the absolute difference between two percentages, while percent change describes the relative difference.
This distinction matters for interest rates, poll results, and statistics reported in the news. State whether a figure is a change in percentage points or a percent change so the meaning is unambiguous.
Common Percent Mistakes
Forgetting to divide the percent by 100
15% is 0.15 as a decimal. Multiplying by 15 instead of 0.15 gives an answer 100 times too large.
Dividing by the new value for percent change
Percent change divides by the original value, not the new value. The denominator is always the starting amount.
Confusing percentage points with percent change
Moving from 40% to 50% is 10 percentage points but a 25% relative increase.
Reversing part and total
For “A is what percent of B,” divide the part A by the total B, not the other way around.
Chaining discounts by adding percentages
A 20% discount followed by a 10% discount is not 30% off. Apply each factor in turn: 0.80 × 0.90 = 0.72, a 28% discount. The Discount Calculator stacks those markdowns for you.
Percent Calculator FAQs
How do I find a percent of a number?
Divide the percent by 100 and multiply by the number. For 15% of 200, compute 0.15 × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the total and multiply by 100. For 30 out of 200, compute (30 / 200) × 100 = 15%.
How is percentage change calculated?
Subtract the original value from the new value, divide by the original value, and multiply by 100.
What is the difference between percent change and percentage points?
Percentage points measure the absolute gap between two percentages. Percent change measures the relative change from the original value.
Can I use negative or decimal values?
Yes. The calculator accepts finite decimals and negatives, though a total or starting value of zero is undefined for some modes.
Are my values sent to a server?
No. The calculation runs locally in your browser.
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Reviewed by Prof. Dr. Khalil Mudassar (PhD) · Last updated: [mc_modified_date]
Sources
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Disclaimer
This calculator is intended for general educational and practical use. Review important results before relying on them in professional work.