About this tool
The Percentage Calculator handles the three percentage questions people run into most often: finding what a given percentage of a number equals, figuring out what percentage one value is of another, and calculating the percentage increase or decrease between two numbers — handy for discounts, raises, exam scores, or tracking changes over time. Pick the mode that matches your question, type in the numbers, and the result updates immediately along with the step-by-step formula used to reach it, so you can see exactly how the math works rather than just getting a bare answer. Everything runs locally in your browser as you type, with a one-click copy button for the final result.
How to use
- 1
Pick a Calculation Mode
Choose percentage of a number, ratio comparison, or percentage change.
- 2
Enter Your Numbers
Type the relevant values into the input fields.
- 3
Read the Result
The answer and the formula used to calculate it appear immediately.
Features
- Mode 1: Calculate what is X% of Y
- Mode 2: Calculate what percentage X is of Y
- Mode 3: Calculate percentage increase or decrease from X to Y
- Step-by-step formula shown alongside the final result
- Updates instantly as you type, no submit button needed
- One-click copy of the result to your clipboard
Tips & common mistakes
- •For discounts, use Mode 1 (X% of Y) to find the amount taken off, then subtract it from the original price yourself if the tool doesn't show the final price directly.
- •A common mistake is mixing up "percent of" with "percent change" — use Mode 3 specifically when comparing an old value to a new one.
- •Percentage change is always calculated relative to the original (old) value, not the new one, which is why the order you enter numbers in matters.
- •A negative result in Mode 3 means a decrease, not an error — read the sign as part of the answer.
Core Percentage Formulas
All three modes are variations on the same underlying relationship between parts, wholes, and 100.
X% of Y = (X × Y) / 100 | % Change = ((New − Old) / Old) × 100- •Percentage value: (Percentage / 100) × Base number
- •Fraction to percentage: (Part / Whole) × 100
- •Percentage change: ((Final − Initial) / Initial) × 100