Percentage Calculator with 5 Modes
This percentage calculator solves the everyday percent problems in one place: what is X% of Y, what percent X is of Y, increasing or decreasing a value by a percentage, percent change, and percent difference. Pick a mode, type your numbers, and the answer appears instantly with the formula spelled out below it.
It is built for anyone who works with percentages: students figuring out test scores and grades, shoppers checking sale prices and discounts, and business owners working out markups, margins, and price changes. Decimal inputs like 12.5% or 99.99 are supported throughout.
How to Use the Percentage Calculator
Choose a calculation mode
All five modes are visible on screen at once. Go straight to the one that matches your problem — from "What is X% of Y?" to "Percent Difference".
Enter your values
Type your numbers into the input fields. On the percent field for "What is X% of Y?" and "Increase/Decrease", focus an empty box to get a preset dropdown of common values (5%, 10%, 15%, 20%, 25%, 50%).
Read the live result
The result updates automatically as you type. For Percent Change, an Increase or Decrease badge shows the direction of the move.
Check the formula and copy
Each result shows its step-by-step formula underneath. Use the swap button to exchange two values, the Example button to see a real use case, and the copy button to send the result to your clipboard.
Five Complete Calculation Modes
What is X% of Y?
Find a percentage of any number — perfect for tips, taxes, and discounts. Formula: X ÷ 100 × Y. Example: 20% of 150 = 30.
X is What Percent of Y?
Find what percentage one number is of another — great for test scores and ratios. Formula: X ÷ Y × 100. Example: 45 is 75% of 60.
Increase or Decrease by %
Add or subtract a percentage from a base value for markups and discounts. Increase: Value + (Value × % ÷ 100). Example: $80 decreased by 25% = $60.
Percent Change
Measure the increase or decrease between two values, with an Increase or Decrease badge. Formula: (New − Old) ÷ |Old| × 100. Example: $40 to $52 = +30%.
Percent Difference
Find the relative difference between two values without a direction. Formula: |A − B| ÷ ((|A| + |B|) ÷ 2) × 100. Example: 45 vs 55 = 20%.
Additional Features
Live Calculation
Results update instantly as you type — no calculate button to press.
Preset Percentages
Quick-pick common values (5%, 10%, 15%, 20%, 25%, 50%) from a dropdown on empty percent fields.
Step-by-Step Formulas
Every result shows the exact formula it used, with numbers and operators broken out clearly.
Swap Values
A swap button on the relevant modes exchanges two inputs so you can compare results instantly.
Copy to Clipboard
Copy any result with one click to paste it wherever you need it.
Practical Examples
An expandable Example for each mode explains exactly when to use that calculation.
Dark Mode
A built-in dark theme keeps the calculator comfortable in any lighting.
Fully Private
All math happens locally in your browser — nothing is sent to a server or saved.
Frequently Asked Questions
How do I calculate the percentage of a number?
Use the "What is X% of Y?" mode. Enter the percentage as X and the number as Y, and the calculator multiplies them: X ÷ 100 × Y. For example, 20% of 150 = 30. This also covers tips and taxes — a 15% tip on a $50 bill is 15% of 50 = $7.50.
How do I find what percent one number is of another?
Use the "X is what % of Y?" mode. Enter the part as X and the total as Y; the calculator computes X ÷ Y × 100. This is ideal for test scores: 45 correct out of 60 questions is 45 is 75% of 60.
How do I calculate a percentage increase or decrease?
Use the "Increase/Decrease by %" mode. Choose Increase or Decrease, enter the base value, then the percentage. To apply a discount, select Decrease — a $100 item with 20% off becomes $80. For a markup, select Increase.
What is the difference between percent change and percent difference?
Percent change measures how much a value rose or fell from an original value, so it has a direction (an Increase or Decrease badge). Percent difference compares two values without treating either as the "original" — it simply measures how far apart they are, using the average of the two as the baseline.
What happens if I divide by zero?
The calculator handles it gracefully by showing "-" instead of an error. This can happen in Percent Change when the original value is 0, or in Percent Difference when both values are 0.
Can I use decimal numbers?
Yes. Every input accepts decimals, so you can enter values like 12.5% or 99.99. Results are shown to up to six decimal places, with trailing zeros removed for a clean readout.
Why does the preset dropdown not appear?
The preset dropdown only opens when the percent field is empty. If you have already typed a value, clear it first and focus the field again to see the common percentages.
Is my data saved anywhere?
No. Every calculation happens locally in your browser. Your numbers are never sent to any server, and no calculation history is stored.
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