Calculate Online Percentage
Every everyday percentage question comes down to one of four patterns. Pick the one that matches your problem below — each calculator shows the answer and the arithmetic so you can check it or copy it into homework.
What is X% of Y?
- 15% of 240
- 36
- As a decimal multiplier
- 240 × 0.15
Steps
- 15 ÷ 100 = 0.15
- 0.15 × 240 = 36
X is what percent of Y?
- 18 is this percent of 24
- 75%
- Fraction
- 18/24 = 0.75
Steps
- 18 ÷ 24 = 0.75
- 0.75 × 100 = 75%
X is P% of what?
- 30 is 20% of
- 150
Steps
- 20% = 0.2
- 30 ÷ 0.2 = 150
- Percent change
- -25%
- Direction
- Decrease
- Percent difference (symmetric)
- 28.5714%
- Absolute change
- -20
Steps
- (60 − 80) ÷ |80| × 100 = -25%
Worked example
Example: a 15% tip on a $64 dinner
- Convert 15% to a decimal: 15 ÷ 100 = 0.15
- Multiply: 0.15 × 64 = 9.60
The tip is $9.60, for a total of $73.60.
Formula
Part = Percent ÷ 100 × Whole
Percent = Part ÷ Whole × 100
Whole = Part ÷ (Percent ÷ 100)
These are the same equation rearranged. If you know any two of part, whole and percent, you can find the third.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 30% of 250 = 0.30 × 250 = 75.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. 12 out of 20 = 12 ÷ 20 × 100 = 60%.
Is X% of Y the same as Y% of X?
Yes. 8% of 50 equals 50% of 8 — both are 4. Flipping them can make mental math much easier.
How do I turn a fraction into a percent?
Divide the numerator by the denominator and multiply by 100. 3/8 = 0.375 = 37.5%.
Last reviewed October 17, 2026 · Calculations run in your browser; nothing you enter is sent to a server.