Percentage Calculator
Calculate percentages, percentage increases, decreases, and fractions with step-by-step mathematical breakdowns.
What is P% of X?
Find a percentage of a number. E.g. What is 15% of 200?
X is what % of Y?
Find what percentage one number is of another. E.g. 30 is what % of 150?
% Change from A to B
Calculate percentage increase or decrease between two values. E.g. 80 → 100
How to Use Percentage Calculator
- Select Calculation Mode: Choose from: 'What is P% of X?', 'X is what % of Y?', or '% Change from A to B'.
- Enter Numbers: Type your values into the corresponding input fields. Results compute automatically in real-time.
- View Formula Breakdown: Review the step-by-step mathematical formula shown directly beneath the calculated answer.
- Copy Result: Click 'Copy' next to any result card to paste the number wherever you need.
Frequently Asked Questions
How do I calculate percentage increase or decrease?
To find percentage change from A to B: subtract original value A from new value B, divide by original value A, and multiply by 100. Our third calculator panel automates this with increase/decrease badges.
Does the calculator handle negative numbers and decimals?
Yes, all three calculator panels accept positive, negative, and floating-point decimal numbers.
How do I calculate sales tax or discounts?
Use the 'What is P% of X?' panel. For a 20% discount on a $150 item, calculate 20% of 150 ($30), then subtract from original price.
Why do calculations update instantly as I type?
We attach real-time input event listeners so you don't need to manually click Calculate buttons.
How are rounding errors handled?
Results are rounded cleanly to 4 decimal places where necessary to eliminate JavaScript floating point inaccuracies (such as 0.1 + 0.2 = 0.30000000000000004).
Can I use this on my mobile phone?
Yes, the layout adapts into a clean single-column mobile view with touch-friendly input fields.