Percentage Calculator
What is X% of Y, percentage increase and decrease, and test score percentages — for students.
Results are calculated instantly in your browser — nothing you enter is sent anywhere. Test-score letter grades use the simple scale A 90+, B 80–89, C 70–79, D 60–69, F below 60; your school may use a different scale. For a full grade-point result, try the GPA calculator.
Percentage formulas at a glance
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | (X ÷ 100) × Y | 20% of 150 = 30 |
| X is what % of Y? | (X ÷ Y) × 100 | 30 is 20% of 150 |
| Percentage increase / decrease | ((New − Old) ÷ Old) × 100 | 50 to 75 = +50% |
| Test score percentage | (Earned ÷ Total) × 100 | 42 of 50 = 84% (B) |
Percentage calculator for students & test scores
A percentage calculator turns a "what is X percent of Y" question into an answer in one step — and this one also handles percentage increase, percentage decrease, and test score percentages with a letter grade. Students use it most often after a test or quiz: enter the points you earned and the total points possible, and you get your percentage and your letter grade right away.
The four modes cover the questions that come up again and again. "What is X percent of Y" is the classic — a tip, a discount, or a share of a total. "X is what percent of Y" flips it around: how much of the whole did you get? Percentage increase and decrease compare two values, which is how you measure a price rise, a score improvement, or a drop in marks. The test score mode is the student-first one: it divides earned points by total points and converts the result to the simple A–F scale.
Everything runs in your browser, so your scores stay private. If you need grade points rather than just a letter, use the grade calculator or the GPA calculator to convert percentages into GPA points.
How the percentage calculator works
Four questions, one idea: part divided by whole, times 100. "What is 20% of 150?" is 150 x 0.20 = 30. "30 is what percent of 150?" is 30 / 150 x 100 = 20%. Percentage change is (new - old) / old x 100 — 50 to 75 is +50%, 80 to 60 is -25%.
The test-score mode turns earned marks into a percentage and a letter grade: 42 out of 50 is 84%, a B. It is the same maths teachers use when they mark a test.
Need a letter grade from weighted assignments? Use the grade calculator.
How to use the percentage calculator
- Choose what you want to work out: what is X% of Y, X is what % of Y, percentage increase / decrease, or a test score percentage.
- Enter the two numbers the mode asks for — for a test score, that is the points you earned and the total points possible.
- Press Calculate percentage to see the answer, and the letter grade for test scores.
- Switch modes any time — the calculator keeps your numbers in the other fields.
Frequently asked questions
How do I work out what is X percent of Y?
Divide X by 100, then multiply by Y. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. Choose the "What is X% of Y?" mode above and the calculator does it for you.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 is (30 ÷ 150) × 100 = 20% of 150. Use the "X is what % of Y?" mode above.
How do I calculate a percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 50 to 75 is ((75 − 50) ÷ 50) × 100 = +50%. A negative answer means a percentage decrease — 80 to 60 is −25%.
How do I work out my test score percentage?
Divide the points you earned by the total points possible and multiply by 100. Scoring 42 out of 50 is (42 ÷ 50) × 100 = 84%, which is a B on the simple scale used here (A 90+, B 80–89, C 70–79, D 60–69, F below 60).
What letter grade is 84%?
On the simple scale this calculator uses, 84% is a B (80–89%). Some schools use plus/minus grades — 84% would be a B on the standard scale — so check your school's scale if you need the exact grade.
What is the difference between percentage points and percent?
A rise from 50% to 60% is a 10 percentage-point rise, but a 20% increase (10 ÷ 50 × 100). Percentage points measure the plain difference; percent measures the difference relative to where you started.
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