This percentage calculator covers the five calculations people search for most: percent of an amount, what percent a part is of a whole, the result of a percentage increase or discount, and the percent change between two values. Every result comes with the step-by-step working, so it doubles as a quick answer and as a way to understand the formula behind it.
Everything runs in your browser, accepts numbers typed with a comma or a period, and lets you choose how many decimals to show — handy for everyday math as well as for schoolwork that needs an exact figure.
How to use
- 1Pick the calculation you need: percent of a number, what percent one number is of another, an increase, a decrease, or the percent change between two values.
- 2Type the numbers into the fields; both a comma and a period work as the decimal separator.
- 3Read the result instantly, and turn on “Show steps” to see the full working.
- 4Adjust the decimal precision or thousands separator, then copy the result with one click.
What you can do
- Percent of an amount
- What percent one number is of another
- Percentage discounts and increases
- Percent change between two values
What percentage calculations are used for
Percentages show up in discounts, taxes, commissions, raises, statistics and grades. Doing the math by hand is easy to get wrong, especially with decimals or when you need to reverse the operation — for instance, finding the total when you only know what a percentage of it is worth.
- Work out the real discount on a sale, or the final price after a price increase.
- Check what percentage of a goal, budget or target has already been reached.
- Compare two periods or two figures and express the difference as a percent change.
- Recover a total when only the value of a percentage of it is known.
The formula behind each mode
Each mode answers a different question with its own formula. Knowing them helps you pick the right mode without trial and error.
- Percent of a number: result = base × (percent ÷ 100).
- What percent a part is of a whole: percent = (part ÷ base) × 100.
- Percentage increase: new value = base × (1 + percent ÷ 100).
- Percentage decrease: new value = base × (1 − percent ÷ 100).
- If a percentage is worth A, the total is: total = A ÷ (percent ÷ 100).
- Percent change between two values: ((final value − initial value) ÷ initial value) × 100.
Common percentage mistakes
Most errors come from confusing what the base is, not from the formula itself. For example, if a price rises 20% and then drops 20%, it does not return to the original price: each percentage is applied to a different base.
- Percentage points are not the same as percent: going from 20% to 25% is 5 percentage points, but a 25% increase over 20%.
- Applying a discount and then the same percentage increase does not bring you back to the starting value.
- When reversing a percentage (the “Total” mode), remember the percentage can't be 0.
Frequently asked questions
How do I calculate 15% of a number?
Multiply the number by 15 and divide by 100 (or multiply it directly by 0.15). For example, 15% of 200 is 200 × 0.15 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 40 out of 200 is (40 ÷ 200) × 100 = 20%.
How do I calculate a discount quickly?
Multiply the price by the discount percentage and divide by 100 to get the savings, then subtract that from the original price. The “Decrease” mode does both steps at once.
What's the difference between percent change and percentage of a total?
Percentage of a total shows what share one amount represents of another at a single point in time. Percent change compares two values — like this month's sales versus last month's — and expresses how much things moved between them.
Does it work with decimals and negative numbers?
Yes. It accepts a comma or a period as the decimal separator and negative values, and you can choose how many decimals to show with the precision control.
Why does the “Total” mode give no result when the percentage is 0?
Because dividing by a 0% percentage is the same as dividing by zero, which has no mathematical result. Enter a non-zero percentage to recover the total.