Percentage Calculator
Three calculators in one: percent of a number, percentage change, and ratio.
What is X% of Y?
Percentage Change
X is What % of Y?
How it works
Three simple steps —everything happens in your browser.
Choose your calculation
Pick from: what is X% of Y, X is what % of Y, or % change from X to Y.
Enter your numbers
Type the values into the input fields. Results update instantly as you type.
Copy the result
Click the result to copy it to your clipboard for use elsewhere.
Why choose ToolKnit Percentage Calculator?
Three modes in one
Percentage of a number, number as percentage, and percentage change — all in a single tool.
Instant results
No submit button needed. Results calculate live as you type, so you can iterate quickly.
No data leaves your browser
Pure client-side math. Nothing is sent to any server.
Pro Tips
- ● 25% of 200 is the same as 200 × 0.25. The calculator handles this for you.
- ● Percentage change formula: ((New - Old) / |Old|) × 100. Works for both increases and decreases.
- ● To find what percentage X is of Y: (X / Y) × 100. For example, 25 is 12.5% of 200.
Frequently Asked Questions
What kinds of percentage problems can I solve?+
The calculator handles the three most common cases: finding a percentage of a number, calculating percentage change between two values, and determining what percentage one number is of another. Switching between modes takes one click.
How do I calculate a percentage increase?+
Use the percentage change mode and enter the original value as the start and the new value as the end. The result shows a positive percentage for increases and a negative one for decreases.
Can the calculator handle decimals?+
Yes. Both inputs accept decimals to whatever precision you need, and results display with sensible rounding so they remain readable.
Is the calculator suitable for school homework?+
Yes, with one note: many teachers want to see the working. Use the calculator to check answers and confirm method, then write out the steps yourself for full marks.
Does it work on mobile?+
The layout is fully responsive. Inputs stack cleanly on phone screens, the keypad is large enough for finger entry, and results stay visible without scrolling.
You May Also Like
Explore more free browser-based tools —no signup, no uploads.