Percentage Calculator
Calculate percentages with seven modes: percent of, what percent of, increase/decrease, add/subtract percent, and percent difference
Interactive tool
Calculation mode
Find a percentage of a number
Inputs
Result
LiveWhat is a Percentage Calculator?
A percentage calculator computes any of the common percent operations from two simple inputs. This tool covers seven distinct modes: finding a percentage of a number, expressing one number as a percent of another, finding the whole given a percent, computing percent change, adding or subtracting a percent, and computing the symmetric percent difference. Each mode shows the step-by-step formula so you can verify the math at a glance.
How to Use This Percentage Calculator
- 1Pick the calculation mode that matches your problem
- 2Enter the two values for that mode
- 3Read the result and the step-by-step explanation
- 4Copy the result to your clipboard with one click
- 5Switch modes any time to compare formulas
Key features
Seven calculation modes
Cover every common percent question without switching tools
Step-by-step formulas
See exactly how the result was derived, so you can teach or verify
Live evaluation
Results update as you type: no submit button required
Locale-aware formatting
Numbers are formatted with your browser's locale settings
Safe division guards
Friendly error messages when a calculation would divide by zero
Keyboard shortcuts
Copy with Cmd/Ctrl+Enter and clear with Cmd/Ctrl+K
Sample values
Load a realistic example for the active mode in one click
100% private
All math happens in your browser; nothing is uploaded
Why Use a Dedicated Percentage Tool?
Percentages are everywhere: taxes, tips, discounts, growth rates, exam scores, lab results, yet they are easy to compute wrong, especially around increase vs decrease, base vs reference, and difference vs change. A dedicated tool with explicit modes and visible formulas removes that ambiguity and lets you focus on the answer.
Common use cases
- Adding tax (e.g. 8.875% sales tax) to a base price
- Subtracting a discount (e.g. 25% off) from a list price
- Computing year-over-year revenue growth or churn rate
- Finding what percent a part is of a total (e.g. budget allocation)
- Computing the original price before tax or discount
- Comparing two values with a symmetric percent difference
Percent vs percentage point
A percent is a ratio expressed per 100, while a percentage point is the absolute difference between two percent values. If interest rises from 4% to 5%, that is a 1 percentage point increase but a 25% relative increase. The "Increase / decrease" mode computes the relative version.
Increase/decrease vs percent difference
- Increase / decrease: relative to a starting value (asymmetric)
- Percent difference: relative to the average of both values (symmetric)
- Use increase/decrease when there is a clear "before" and "after"
- Use percent difference when comparing two equal-status values
Tips & best practices
Pick the right mode
Read the description of each mode at the top of the page; using the wrong mode is the most common source of percent errors.
Watch out for zero divisors
If your "of" value or starting value is zero, the percent is undefined. The tool will show a friendly error rather than NaN.
Negative values are supported
You can use negative inputs for finance applications such as losses or refunds. The explanation panel reflects the sign correctly.
Round only at the end
Avoid rounding intermediate steps when chaining calculations. The tool keeps full precision internally and rounds only when displaying.
Use copy to keep going
Copy the formatted result with Cmd/Ctrl+Enter, then paste it as the input of another calculation to chain operations.
Privacy & security
This percentage calculator runs entirely in your browser. No values, results, or formulas are uploaded or logged. It works fully offline once the page is loaded.
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Frequently Asked Questions
How do I find X% of a number?
Use the "X% of Y" mode and enter the percent and the base. The result is (X/100) × Y. For example, 20% of 150 = 30.
How do I express one number as a percent of another?
Use the "X is what % of Y" mode. The result is (X/Y) × 100. For example, 30 is 20% of 150.
What is the difference between percent change and percent difference?
Percent change (increase/decrease) is asymmetric and relative to a starting value. Percent difference is symmetric and relative to the average of both values. Use change when there is a clear before and after; use difference when comparing two equal-status values.
Why do I get an error when one input is zero?
Some operations require dividing by an input. If that input is zero, the percent is mathematically undefined. The tool surfaces a friendly error rather than showing NaN or Infinity.
Are negative values supported?
Yes. You can enter negative numbers for any mode. The step-by-step explanation will reflect the signs correctly.
Is my data sent to a server?
No. All computation happens entirely in your browser; no inputs or results are uploaded, logged, or stored anywhere outside your device.