Percentage Calculator
Calculate percentages, convert raw scores to grades, and find percentage change. Instant results.
The percentage calculator handles three core calculations: finding a percentage of a number (e.g. 15% of 200 = 30), calculating what percentage one number is of another (e.g. 45 out of 60 = 75%), and computing percentage change between two values. It also converts raw exam scores to percentages and letter grades.
Convert a raw score to a percentage and letter grade
How to Use the Percentage Calculator
- 1Select the type of percentage calculation you need from the available options.
- 2Enter the required numbers in the input fields.
- 3Click Calculate to instantly see the result.
- 4Click Clear to reset and try a different calculation.
Worked Example: "% of Number" vs. "What % is X of Y?"
These two modes are mirror images of the same relationship, and swapping them is the most common percentage-calculator mistake. % of Number starts with a percentage and a total, and solves for the piece: 15% of 60 = (15 ÷ 100) × 60 = 9.00.
What % is X of Y? runs that same relationship backwards — it starts with the piece and the total, and solves for the percentage: 9 is what % of 60? = (9 ÷ 60) × 100 = 15.00%.
Same three numbers, same relationship — only the unknown changes. If a result looks wildly off, the usual culprit is entering the total in the field meant for the part, or vice versa.
Worked Example: The 50% Up, 50% Down Trap
Using the calculator's own default example — an original value of 50 and a new value of 75 — Percentage Change returns (75 − 50) ÷ 50 × 100 = +50.00%. So far, straightforward.
Now apply a 50% decrease to that new value of 75: 50% of 75 = 37.50, so 75 − 37.50 = 37.50 — not back to 50. Feeding 75 → 37.50 back into Percentage Change confirms the decrease itself was correct: −50.00%. The catch is that the increase and the decrease were each calculated on a different base (50, then 75).
Comparing the final value to the original starting point (50 → 37.50) shows the real net change: (37.50 − 50) ÷ 50 × 100 = −25.00%. A percentage increase and an equal-sized percentage decrease never cancel out — the decrease is always taken from a larger number, so it removes more than the increase added.
Percentage Points vs. Percent Change
If a class average moves from 70% to 84%, it's tempting to call that a "14% increase" because 84 − 70 = 14. That 14 is actually 14 percentage points — the raw gap between the two percentages. Percentage Change measures something different: the relative jump, (84 − 70) ÷ 70 × 100 = +20.00%. Both numbers are correct; they answer different questions — "how many points did it move?" versus "how much bigger is the new number relative to the old one?" This mix-up shows up constantly in interest-rate and tax-rate reporting: a rate moving from 5% to 8% is a 3-point jump, but run through this calculator it's a +60.00% relative increase — very different numbers describing the same move.
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Frequently Asked Questions
How do I calculate a percentage of a number?
To find X% of Y: multiply Y by X, then divide by 100. For example, 15% of 200 = (200 × 15) ÷ 100 = 30.
How do I calculate what percentage one number is of another?
Divide the first number by the second, then multiply by 100. For example, 45 out of 60 = (45 ÷ 60) × 100 = 75%.
How do I calculate percentage change?
Percentage change = ((New Value − Old Value) ÷ Old Value) × 100. A positive result is an increase; a negative result is a decrease.
How do I convert a raw exam score to a grade?
Divide your score by the total possible score, multiply by 100 to get the percentage, then check your institution's grading scale. For example, 42/50 = 84%.