Percentage Calculator
Everyday percent problems, solved five ways. Pick a mode — X% of Y, reverse percentages, increase, decrease, or difference — and see the formula with your answer.
What is X percent of Y?
Formula
(X ÷ 100) × Y
Answer
30.00
20% of 150 = 30.00
Tip: “percentage points” and “percent” are different — going from 10% to 15% is +5 percentage points but a +50% relative increase.
What is X% of Y?
The most common percent question — tips, tax, discounts, and commissions all use it. Convert X% to a decimal (divide by 100) and multiply by Y. 20% of $48.50 is 0.20 × $48.50 = $9.70.
X is what percentage of Y?
Use this when you know the part and the whole: test scores, savings rates, budget shares. Divide X by Y and multiply by 100. Saving $180 of a $900 paycheck is (180 ÷ 900) × 100 = 20%. Always put the part on top.
Percentage increase
Subtract the old value from the new value, divide by the old value, multiply by 100. Rent rising $1,200 → $1,290 is ($90 ÷ $1,200) × 100 = 7.5%. The starting value is always the base.
Percentage decrease
The mirror image: subtract the new value from the old value, divide by the old value, multiply by 100. A price falling $80 → $60 is ($20 ÷ $80) × 100 = 25% off.
Percentage difference
When neither value is clearly the “start” — comparing two prices, two measurements — use the symmetric formula: absolute difference divided by the average of both values, times 100. Between $50 and $65: $15 ÷ $57.50 × 100 ≈ 26.1%.
Change vs. difference
Examples
| Question | Mode | Calculation | Answer |
|---|---|---|---|
| 20% of 150 | X% of Y | 0.20 × 150 | 30 |
| 30 is what % of 120? | Reverse | (30 ÷ 120) × 100 | 25% |
| $22/hr → $24/hr | Increase | (2 ÷ 22) × 100 | 9.09% |
| 180 → 162 lbs | Decrease | (18 ÷ 180) × 100 | 10% |
| 50 vs. 65 | Difference | (15 ÷ 57.5) × 100 | 26.09% |
Frequently asked questions
What is X% of Y?
Divide X by 100 and multiply by Y. 15% of 200 is 0.15 × 200 = 30. Select the “X% of Y” tab above and enter both numbers.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 45 as a percent of 60 is (45 ÷ 60) × 100 = 75%.
How do I calculate percent increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. $50 → $65 is (15 ÷ 50) × 100 = 30% increase.
What’s the difference between percent change and percent difference?
Percent change uses the starting value as the base (directional: increase or decrease). Percent difference uses the average of both values as the base (symmetric, no direction) — common in science and comparisons.
What are percentage points?
The simple difference between two percentages. A move from 4% to 6% is +2 percentage points but a +50% relative increase. They measure different things.
Educational information only. For educational and informational purposes only. This website does not provide personalized financial, investment, tax, or legal advice.