Percentage Calculator
Pick the type of percentage question you're solving — the fields below change to match.
15% of 200
30
Remaining amount
170
15% of 200 is 30.
Quick answer
A percentage calculator finds part of a whole using part = (percent ÷ 100) × base. This tool also reverses percentages, works out the percentage change between two values, and adds or subtracts a percentage from a number — covering five common percentage questions in one place.
Explore more Maths calculators
Percentage Calculator is one of numbers, percentages and conversion tools on OneCalculate — see the full set for this category.
Browse MathsHow it works
This percentage calculator covers five of the most common percentage questions, each using its own formula. Pick a mode above and the calculator shows only the two numbers that mode needs.
X% of Y finds part of a number: Result = Y × (X ÷ 100). For example, 15% of 200 is 200 × (15 ÷ 100) = 30.
X is what % of Y expresses one number as a percentage of another: Result = (X ÷ Y) × 100. For example, 30 is
(30 ÷ 200) × 100 = 15% of 200.
% change from X to Y finds the percentage increase or decrease between two values:
Result = ((Y − X) ÷ X) × 100. For example, going from 80,000 to 92,000 is ((92,000 − 80,000) ÷ 80,000) × 100, a
15% increase. A negative result means a decrease rather than an increase.
Add X% to Y increases a number by a percentage: Result = Y × (1 + X ÷ 100). For example, adding 15% to 200
gives 200 × 1.15 = 230.
Subtract X% from Y decreases a number by a percentage: Result = Y × (1 − X ÷ 100). For example, subtracting
15% from 200 gives 200 × 0.85 = 170.
Reversing a percentage — working backwards from a result to the original number — uses the same two formulas run in reverse. Divide 230 by 1.15 and you’re back to 200; divide 170 by 0.85 and you’re back to 200 as well. That’s the trick behind every reverse percentage calculator: undo the multiplication instead of repeating it.
Worked example
Maya has dinner with two friends at a restaurant in Melbourne, and the bill comes to $184. She wants to leave a 15% tip before splitting the total evenly three ways.
Using Add X% to Y: 15% of $184 is $184 × 0.15 = $27.60, so the bill with tip comes to $184 × 1.15 = $211.60 — $70.53 each.
A few months later, Maya’s manager tells her that her annual salary is moving from $80,000 to $92,000, and she wants to know exactly how big that raise is in percentage terms.
Using % change from X to Y: ($92,000 − $80,000) ÷ $80,000 × 100 = 15%. Maya’s pay rise works out to the same 15% as her dinner tip — a reminder that a percentage only tells you the relative size of a change, not the dollar amount behind it.
| Scenario | Mode used | Calculation | Result |
|---|---|---|---|
| Dinner bill with tip | Add X% to Y | $184 × 1.15 | $211.60 |
| Annual salary rise | % change from X to Y | ($92,000 − $80,000) ÷ $80,000 × 100 | 15% |
Frequently asked questions
How do you calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100 — for example, 15% of 200 is (15 ÷ 100) × 200, which equals 30. You can also convert the percentage to a decimal first, 0.15, then multiply by 200. Both orders give the same result, since multiplication is commutative.
How do you calculate percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. For example, a rise from $80,000 to $92,000 is (92,000 − 80,000) ÷ 80,000 × 100, which equals 15%. A negative result means the value decreased rather than increased.
How do you reverse a percentage?
Divide the new value by (1 + percent ÷ 100) if it increased, or by (1 − percent ÷ 100) if it decreased, to reverse a percentage back to its original number. For example, $230 after a 15% increase reverses to $230 ÷ 1.15, which is $200. This undoes the multiplication used to apply the percentage in the first place.
What is the difference between percentage change and percentage points?
Percentage change is a relative measure, while percentage points measure the raw gap between two percentages. Going from 20% to 25% is a 25% percentage change, since (25 − 20) ÷ 20 × 100 equals 25, but it's only a 5 percentage point increase. The two figures are rarely the same number.
How do you calculate what percentage one number is of another?
Divide the relevant number by the total, then multiply by 100. For example, if 30 people out of 200 attended an event, that's (30 ÷ 200) × 100, which equals 15%. The same formula works for test scores, discount amounts, survey results and any “X out of Y” question you come across.
How do I add or subtract a percentage from a number?
To add a percentage, multiply the number by (1 + percent ÷ 100); to subtract one, multiply by (1 − percent ÷ 100). For example, adding 15% to 200 gives 230, while subtracting 15% from 200 gives 170. This is how tips, discounts and price markups are usually worked out.
Why does increasing by 10% then decreasing by 10% not return the original number?
Because each percentage is calculated on a different base. Increasing 100 by 10% gives 110, but decreasing 110 by 10% gives 99, not 100, since the second 10% is worked out on the larger number. This is a common source of confusion in percentage problems, and it's why the order matters.
Related calculators
Written and verified by Nirbhay Tripathi
Last updated 18 August 2026
All rates on this page are verified againstKhan Academy — Percentageson 18 August 2026. See our methodology for the full update calendar.