How does the percentage calculator work?

Pick the type of percentage problem you have, enter your numbers, and it instantly calculates the answer and shows the working. There are five modes: finding X% of a number, finding what percentage one number is of another, calculating percentage change, adding or subtracting a percentage, and finding the whole from a part and its percentage.

Is the percentage calculator free?

Completely free. No sign-up, no downloads, no limits — use it as much as you need.

What types of percentage problems can it solve?

It covers five common cases: (1) what X% of a number is, (2) what percent one number is of another, (3) the percentage increase or decrease between two numbers, (4) adding or subtracting a percentage from a number, and (5) finding the whole when you know the part and what percentage it represents.

How do I find what percentage one number is of another?

Use the 'What % is X of Y?' mode. Enter the part and the whole, and it divides the part by the whole and multiplies by 100. For example, 16 is 20% of 80 because 16 ÷ 80 × 100 = 20.

How is percentage change calculated?

Percentage change = (new value − original value) ÷ original value × 100. A positive result means an increase, a negative result means a decrease. For example, going from 80 to 100 is a +25% change; going from 100 to 80 is a −20% change.

How do I add or subtract a percentage?

Use the 'Add / Subtract %' mode and choose Add or Subtract. To add P% to a number Y, the formula is Y × (1 + P/100). To subtract P%, it's Y × (1 − P/100). This is useful for discounts, tips, tax, and markups.

Can it work backwards from a percentage to find the whole?

Yes. The 'Reverse %' mode finds the original total when you know a part and what percentage of the whole it represents. The formula is: whole = part ÷ (percentage ÷ 100). For example, if 16 is 20% of something, the whole is 16 ÷ 0.2 = 80.

Does it show the calculation steps?

Yes — each result shows the equation used, so you can see exactly how the answer was reached. This is useful for checking your work or understanding the method.

Is my data stored or sent anywhere?

No. All calculations run directly in your browser. Nothing is stored or sent to a server.

Does it work on mobile?

Yes, it's fully responsive. The mode tabs and input layout adapt to smaller screens without horizontal overflow.

Percentage Calculator — FAQ

Answers to common questions about the percentage calculator and how each mode works.

How does the percentage calculator work?

Pick the type of percentage problem you have, enter your numbers, and it instantly calculates the answer and shows the working. There are five modes: finding X% of a number, finding what percentage one number is of another, calculating percentage change, adding or subtracting a percentage, and finding the whole from a part and its percentage.
Is it free?

Completely free — no sign-up, no downloads, no limits. Use it as much as you need.
What types of percentage problems can it solve?

Five common cases: (1) what X% of a number is, (2) what percent one number is of another, (3) the percentage increase or decrease between two numbers, (4) adding or subtracting a percentage from a number, and (5) finding the whole when you know the part and the percentage it represents.
How do I find what percentage one number is of another?

Use the What % is X of Y? mode. Enter the part and the whole, and it divides the part by the whole and multiplies by 100. For example, 16 is 20% of 80 because 16 ÷ 80 × 100 = 20.
How is percentage change calculated?

Percentage change = (new value − original value) ÷ original value × 100. A positive result is an increase; a negative result is a decrease. For example, going from 80 to 100 gives +25%; going from 100 to 80 gives −20%.
How do I add or subtract a percentage?

Use the Add / Subtract % mode and pick Add or Subtract. To add P% to Y the formula is Y × (1 + P/100). To subtract P% it's Y × (1 − P/100). This is useful for discounts, tips, tax, and markups.
Can it work backwards from a percentage to find the whole?

Yes. The Reverse % mode finds the original total when you know a part and what percentage of the whole it represents. Formula: whole = part ÷ (percentage ÷ 100). If 16 is 20% of something, the whole is 16 ÷ 0.2 = 80.
Does it show calculation steps?

Yes — each result shows the equation used so you can see exactly how the answer was reached. Useful for double-checking or understanding the method.
Is my data stored or sent anywhere?

No. All calculations run directly in your browser. Nothing is stored or sent to a server.
Does it work on mobile?

Yes — fully responsive. The mode tabs and input layout adapt to smaller screens without horizontal overflow.

Use the Percentage Calculator