Percentage Calculator
Pick a calculation and enter two numbers. The answer and formula appear instantly.
- Result
- —
Everything is calculated in this page. Answers are shown to up to 4 decimal places.
How to use
- 1. Pick a calculationWhat is B% of A, A is what % of B, percent change, or increase/decrease by %.
- 2. Enter two numbersCommas and the % sign are fine.
- 3. Read the answerYou also get the formula used, so you can check the math.
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is B% of A? | A × B ÷ 100 | 15% of 200 → 30 |
| A is what % of B? | A ÷ B × 100 | 30 of 200 → 15% |
| Percent change from A to B | (B − A) ÷ A × 100 | 80 to 100 → +25% |
| Increase / decrease A by B% | A × (1 ± B ÷ 100) | 1,000 minus 20% → 800 |
Discounts and markups
20% off means multiplying by 0.8: $1,000 becomes $800. A 20% markup means multiplying by 1.2: $1,000 becomes $1,200.
Taking 20% off and then adding 20% does not get you back to where you started ($1,000 → $800 → $960), because each percent applies to the current amount.
FAQ
Who is this percentage calculator for?
Shoppers and shop staff checking sale prices, sales and finance teams working out growth or how much of a target has been reached, students and teachers turning scores into percentages, and anyone who wants to check a “up 15%” figure in the news.
When is it useful?
For example, finding the price of a $79.99 item at 30% off, working out what percent 86 is of a target of 100, measuring the percent change from last month’s sales to this month’s, or finding 15% of 200.
What are the benefits of using it?
The four most common percentage calculations are in one place: pick one and enter two numbers. The formula is shown with every answer, so you can check the math or show someone how you got it.
How do I calculate a discount?
Choose “Increase / decrease by %”, then “decrease”. 20% off $1,000 is $800.
How is percent change calculated?
(new − old) ÷ old × 100. From 80 to 100 is 20 ÷ 80 × 100 = a 25% increase. The answer also says whether it is an increase or a decrease.
Which of the four calculations should I use?
“What is 15% of 200?” → “What is B% of A?”. “30 is what percent of 200?” → “A is what % of B?”. “What is the change from 80 to 100?” → “Percent change”. “What is 1,000 minus or plus 20%?” → “Increase / decrease by %”.
What is the difference between percent and percentage points?
If a rate goes from 10% to 12%, it rose by 2 percentage points, which is a 20% increase (2 ÷ 10 × 100).
If I take off 20% and then add 20%, do I get back the original?
No. $1,000 minus 20% is $800, and $800 plus 20% is $960, because each percent applies to the current amount.
How many decimals are shown?
Up to 4 decimal places, rounded. Tiny floating-point errors, like the one in 0.1 + 0.2, are removed before the answer is shown.
Can I type commas or the % sign?
Yes. Numbers like “1,980” or “15%” are fine. Thousands separators and the % sign are ignored and only the number is read.
Can I use negative numbers?
Yes. Put a minus sign in front. In “Percent change”, if the starting number is negative, the change is divided by its absolute value (the number without the minus).
Why is the result “—”?
No answer is shown when it would mean dividing by zero: in “A is what % of B?” when B is 0, and in “Percent change” when the starting number is 0. It also shows “—” if an input can’t be read as a number.
Can I find the original price from a discounted price?
There is no reverse calculation. If the price is $800 after 20% off, divide by (1 − 20 ÷ 100): 800 ÷ 0.8 = $1,000.
Can I copy the result?
Yes. “Copy result” copies the answer as shown. In “Percent change”, the word “increase” or “decrease” is copied too.
Are the numbers I enter sent anywhere?
No. Everything is calculated in your browser.
Does it work on a phone?
Yes. Tapping an input opens a number keyboard. On narrow screens, the answer appears below the inputs.
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