Percentage Calculator
Calculate a percentage, percentage change, or reverse percentage in one place. Use this free tool to solve everyday percentage questions in seconds.
Last updated: 2026-01-08
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Percentage calculator
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Result
50.00
25% of 200 equals 50.
Calculation History (0)
Examples you can apply
Tap an example to prefill the calculator with realistic values.
Percent of a Number
Restaurant Tip
20% of $85
Standard tip calculation for good service.
Result: $17.00
Discount Savings
15% of $250
Estimate how much you save during a sale.
Result: $37.50
Sales Tax
8.25% of $1,500
Calculate tax on a larger purchase.
Result: $123.75
Percentage Change
Investment Return
$100 to $135
Track growth on a stock investment over time.
Result: +35% increase
Weight Loss
180 lbs to 165 lbs
Measure progress toward a health goal.
Result: -8.33% decrease
Price Increase
$3.50 to $4.20
Understand inflation on everyday items.
Result: +20% increase
Reverse Percentage
Test Score
45 is 90% of what?
Find the full score from a percentage grade.
Result: 50
Original Price
$80 is 80% of what?
Determine the pre-discount price of an item.
Result: $100.00
Commission Total
$500 is 5% of what?
Back into a total sale from a commission payout.
Result: $10,000.00
How Percentage Calculations Work
Percentages express a number as a fraction of 100. The word percent literally means per hundred. Understanding three fundamental percentage operations helps solve most everyday math problems.
Finding a Percentage of a Number
Multiply the number by the percentage expressed as a decimal. For 25% of 200: 200 x 0.25 = 50.
Calculating Percentage Change
Divide the difference between two values by the original value, then multiply by 100. Going from 80 to 100 is a 25% increase: ((100 - 80) / 80) x 100 = 25%.
Reverse Percentage (Finding the Base)
When you know a value and what percentage it represents, divide by that percentage as a decimal. If 45 is 15% of something: 45 / 0.15 = 300.
Key tips
- Always identify which number is the base (the 100% reference).
- Percentage increase and decrease are not symmetric; a 50% increase followed by a 50% decrease does not return to the original.
- Percentages above 100% mean the value exceeds the base.
Percentage calculator FAQs
Answers to common questions about percentage math.
How do I calculate what percentage one number is of another?
To find what percentage X is of Y, divide X by Y and multiply by 100. For example, if you scored 45 out of 50 on a test: (45 / 50) x 100 = 90%. You can use our reverse percentage mode by entering the part as the value and solving for what percentage it represents of the whole.
What is the formula for percentage change?
Percentage change = ((New Value - Original Value) / |Original Value|) x 100. The absolute value in the denominator ensures the direction of change is shown in the result sign. A positive result means increase; negative means decrease. From $100 to $75 is -25%, indicating a 25% decrease.
Can I calculate percentage change from zero?
No, percentage change from zero is mathematically undefined because it requires division by zero. When your starting value is zero, percentage change has no meaning. In real-world contexts, you might note this as infinite growth or simply report the absolute change instead. Our calculator will display an explanatory message rather than an error.
How do I reverse-calculate an original price from a sale price?
If an item is discounted by 20%, the sale price represents 80% of the original. Use reverse percentage: divide the sale price by 0.80 (or 80 / 100). For a $60 item after 25% off: $60 / 0.75 = $80 original price. The key is recognizing that the sale price equals (100% - discount%) of the original.
Why does a 50% increase followed by 50% decrease not equal the original?
Percentage changes are relative to different bases. Starting with 100: a 50% increase gives 150 (100 x 1.5). Then a 50% decrease from 150 gives 75 (150 x 0.5), not 100. The decrease is calculated from the larger number. This asymmetry is crucial in finance; a 50% portfolio loss requires a 100% gain to recover.
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Disclaimer
This calculator is for educational and general informational purposes only. Results are estimates based on the formulas and inputs provided. For financial decisions, consult a qualified professional. Calc Hub is not responsible for errors or decisions made based on calculator results.