Percentage Calculator
Four small calculators for the everyday percentage questions, each answered as you type and showing its working.
Worked out on your device as you type; nothing is sent or saved.
Percentages, worked out and shown
Percentages turn up in test scores, survey results and recipes made for more people. This page answers the four everyday percentage questions, each in its own box, so you can answer the one you have without rearranging a formula. Every answer shows its working, so you can check it or reuse the method.
How to use it
- Find the box that matches your question.
- Type the two numbers. A percentage can be typed with or without the % sign.
- Read the answer, the sentence that explains it, and the working.
- Choose how many decimal places answers are rounded to; the default is 2.
The four questions
- X% of Y: divide X by 100, then multiply by Y. 15% of 80 is 12.
- X is what percent of Y: divide X by Y, then multiply by 100. 18 right answers out of 24 is 75%.
- Change from X to Y: divide the difference by the starting value, then multiply by 100. Going from 4 servings to 6 is an increase of 50%; from 6 back to 4 is a decrease of about 33.33%.
- X is Y% of what: divide X by Y, then multiply by 100. If 30 people are 60% of a group, the group has 50.
Good to know
- Up and down aren’t mirror images: a 50% rise followed by a 50% fall leaves 75% of where you started, because the fall is taken from the bigger number.
- Percent and percentage points: going from 40% to 50% is a rise of 10 percentage points, but a 25% increase. Type 40 and 50 in the change box to see the second figure.
- Exact working: numbers are worked out exactly and rounded only at the end, and the sentence says “about” when an answer was rounded.
- Working back from a rise: if a number went up 20% to 60, the last box finds the start: 60 is 120% of 50.
- Dividing by zero has no answer, so a 0 in the wrong place gets a message instead of a wrong number.
- Negative starting values: the change is divided by the starting value’s size, so a rise from −40 to −10 shows as an increase.
Scoring a test you made? The Quiz Creator builds the quiz in the first place.
Frequently asked questions
How do I work out a percentage of a number?
Divide the percentage by 100, then multiply by the number: 15% of 80 is 15 ÷ 100 × 80 = 12. The first box does this for you and shows the working.
How is percentage change worked out?
Subtract the starting value from the new one, divide by the starting value, and multiply by 100. From 40 to 50 is (50 − 40) ÷ 40 × 100 = 25, an increase of 25%. A decrease comes out with a minus sign.
Why can’t it work out a change from 0?
A percentage change divides by the starting value, and dividing by zero has no answer. The tool says so and shows the plain difference instead of a made-up percentage.
Is anything saved or sent?
No. The answers are worked out on this page, on your device. Nothing you type is logged, sent, saved or put in the page address.