Everyday Calculators
Percentage Calculator
Calculate percent of a number, reverse percentages, known-rate adjustments, percentage change, and percentage difference.
Enter the values and review the result.
Calculate percentage
Choose a percentage calculation, enter your values, and see the formula with a step-by-step answer.
Choose a percentage calculation and enter your values.
The result will show the answer, formula, substitution, and short explanation.
Which percentage calculation should you use?
Percent of a number
Use this for questions like: what is 20% of 150?
What percent?
Use this when you know the part and whole, like 30 of 200.
Reverse percentage
Use this when you know that 30 is 20% of an unknown whole.
Apply an increase
Use this when increasing 100 by a known rate such as 20%.
Apply a decrease
Use this when decreasing 100 by a known rate such as 20%.
Percentage change
Use this for before-and-after comparisons, like 40 to 50.
Percentage difference
Use this when comparing two values without a clear old value.
How to find percentage of a number
To find X% of a number, convert the percentage to a decimal and multiply by the number.
X% of Y = X / 100 × Y
20% of 150 = 20 / 100 × 150 = 30
How to apply a percentage increase
Use this mode when the original value and the percentage to add are known. For an old-versus-new comparison, use Percentage Change instead.
Final value = original value × (1 + percentage / 100)
100 increased by 20%: 100 × 1.20 = 120
How to apply a percentage decrease
Use this mode when the original value and the percentage to subtract are known. The tool limits this rate to 100% so the result does not cross below zero through this workflow.
Final value = original value × (1 - percentage / 100)
100 decreased by 20%: 100 × 0.80 = 80
How to solve a reverse percentage
Use the reverse mode when a known part represents a known percentage of an unknown whole.
Whole = part / (percentage / 100)
30 is 20% of what number: 30 / 0.20 = 150
Percentage change vs percentage difference
Percentage change compares an old value to a new value. Percentage difference compares two values using their average as the reference. Use percentage change for before/after changes, and use percentage difference when there is no clear original value.
Percentage change from 80 to 100: (100 - 80) / 80 × 100 = 25%
Percentage difference between 40 and 50: |50 - 40| / ((40 + 50) / 2) × 100 = 22.22%
Common percentage formulas
| Calculation | Formula | Example |
|---|---|---|
| X% of Y | X / 100 × Y | 20% of 150 = 30 |
| X is what percent of Y | X / Y × 100 | 30 of 150 = 20% |
| X is Y% of what number | X / (Y / 100) | 30 is 20% of 150 |
| Increase by X% | original × (1 + X / 100) | 100 increased by 20% = 120 |
| Decrease by X% | original × (1 - X / 100) | 100 decreased by 20% = 80 |
| Percentage change | (new value - old value) / old value × 100 | 80 to 100 = 25% |
| Percentage difference | |A - B| / ((A + B) / 2) × 100 | 80 and 120 = 40% |
Worked examples
What is 20% of 150? 20 / 100 x 150 = 30.
50 increased by 10%: 50 + (50 x 0.10) = 55.
80 decreased by 25%: 80 - (80 x 0.25) = 60.
What percent is 30 of 200? 30 / 200 x 100 = 15%.
30 is 20% of what number? 30 / 0.20 = 150.
Percentage change from 40 to 50: (50 - 40) / 40 x 100 = 25%.
15% of 80: 15 / 100 × 80 = 12.
25 is what percent of 200: 25 / 200 × 100 = 12.5%.
Increase 50 by 20%: 50 × 1.20 = 60.
Decrease 120 by 25%: 120 × 0.75 = 90.
Percentage change from 80 to 100: (100 - 80) / 80 × 100 = 25%.
Percentage difference between 40 and 50: |40 - 50| / ((40 + 50) / 2) × 100 = 22.22%.
Common mistakes
- Dividing by the wrong original value.
- Confusing percentage change with percentage difference.
- Forgetting to multiply by 100.
- Using the new value instead of the original value as the base.
- Treating percentage points and percentages as the same thing.
- Comparing percentages without checking the base values behind them.
- Rounding too early before the final answer.
Real-life uses
Percentage calculations help with discounts and sales, taxes and tips, price increases, grade percentages, finance and interest, business growth, and comparing two values.
For related tasks, try the Discount Calculator, Sales Tax Calculator, Tip Calculator, Percentage Increase Calculator, Percentage Decrease Calculator, and Percentage Change Calculator.
For business and finance examples, compare percent changes with the Profit Margin Calculator, ROI Calculator, or Scientific Calculator.
You can also read the Percentage Calculator Guide and Understanding Percentages, browse Everyday Calculators, explore Math Calculators, or review Business Calculators.
Quick answers
What this calculator answers
- Result: Calculates percent of, what percent, reverse percentage, known-rate increase or decrease, change, and difference.
- Formula: Shows the exact formula and substitution so you can check the math.
- Use cases: Useful for discounts, taxes, tips, grades, price changes, growth, and comparing two values.
- Limit: The change mode uses the old value as its base; percentage difference uses the average of both values.
- Related guide: Review practical percentage formulas and common mistakes. percentage calculator guide
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Results depend on the values you enter and any simplified assumptions used by the tool. Verify important results before making decisions or submitting official information.
Reference check
Sources and references
These references provide background context for the topic. They do not replace official advice or documents for personal decisions.
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Choose the percentage calculation you need.
Enter the values shown for that calculation mode.
Press Calculate Percentage to see the main answer.
Review the formula, substitution, and short explanation.
Switch modes when you need a reverse percentage, known-rate adjustment, change, or difference.
Related Tools
Other helpful tools for percentages, discounts, taxes, tips, and quick calculations.
Percentage Increase Calculator
Apply a known percentage increase to find the increase amount and final value.
Percentage Decrease Calculator
Apply a known percentage decrease to find the reduction amount and final value.
Percentage Change Calculator: Old vs New Value
Compare an original value with a new value to find relative change, direction, and absolute difference.
Discount Calculator
Calculate savings, discounted price, and final price after an optional user-entered tax rate.
Sales Tax Calculator
Calculate sales tax, price after tax, pre-tax price, and checkout totals from an entered rate.
Tip Calculator
Calculate a user-entered tip, tax method, total, and per-person arithmetic without a tipping recommendation.
Profit Margin Calculator
Calculate profit margin, markup, selling price, revenue, cost, and pricing scenarios.
ROI Calculator
Calculate total ROI, gain or loss, return multiple, and an optional annualized endpoint return.
Scientific Calculator
Evaluate numerical expressions with powers, roots, logs, trigonometry, constants, and explicit degree or radian syntax.
Related Guides
Background reading and explanations related to Percentage Calculator.
Frequently Asked Questions
Common questions about Percentage Calculator and how to read the result.
What is a percentage?
A percentage is a number expressed out of 100. For example, 25% means 25 out of 100.
How do I calculate a percentage of a number?
Convert the percentage to a decimal by dividing by 100, then multiply by the number.
How do I find the whole from a part and percentage?
Divide the part by the percentage written as a decimal. For example, 30 / 0.20 = 150.
How does the increase mode work?
It applies a known percentage to one original value. Use Percentage Change instead when you know an old and a new value.
How does the decrease mode work?
It subtracts a known percentage of the original value and limits the decrease to 100%.
What is the difference between percentage change and percentage difference?
Percentage change compares an old value to a new value. Percentage difference compares two values using their average as the reference.
What is the difference between percentage and percentage points?
A percentage is a relative amount. Percentage points describe the direct difference between two percentages, such as 20% to 30% being 10 percentage points.
Why do I multiply by 100?
Multiplying by 100 converts a decimal ratio into a percentage, which means out of 100.
Can percentages be greater than 100?
Yes. A percentage above 100 means the amount is greater than the base value.
Can percentage change be negative?
Yes. A negative percentage change means the value went down from the old value.
Are the results rounded?
Results are formatted for readability, usually up to four decimal places.