This percentage calculator answers one question: what percent is the part of the whole? Divide the part by the whole and multiply by 100. Enter 25 as the part and 200 as the whole, and the result is 12.5%.
People use the words "percentage calculator" for three different jobs: this ratio, "what is X percent of Y," and percent change from an old number to a new one. This form does only the first. The other two formulas are written out below so you can do them by hand without pretending the button did them. The whole must not be zero, because division by zero is undefined.
How to use this calculator
- Enter the part, the number you are measuring.
- Enter the whole, the number you are measuring it against. Do not enter 0.
- Press Calculate. The headline is the part divided by the whole, times 100, with at most two decimal places.
- Read the sentence under the result. It restates the same ratio in words.
How "percent of a whole" is calculated
A percent is a ratio scaled to 100. If the part equals the whole, the result is 100%. If the part is half the whole, the result is 50%. If the part is larger than the whole, the result is above 100%, which is allowed and often correct. 150 out of 80 is more than the whole, so the percent is above 100.
The calculator does not know which number is a price, a score, or a count. It will happily report a percent for any pair except a zero whole. Negative inputs are passed through the same division, which can produce a negative percent. That is rarely what a shopping or grading question wants.
Displayed percents use at most two decimal places. Two divided by three, times 100, is 66.666…%, and the calculator shows 66.67%. The repeating value is not stored as a fraction.
Formula
Percentage = (part ÷ whole) × 100 The whole must not be 0. Related, not what this form computes: X percent of Y = Y × X / 100 Percent change = (new − old) / old × 100
Finding 18% of 85 is the second formula: 85 × 18 / 100 = 15.3. You would not get that by entering part 18 and whole 85. That entry answers a different question and returns 21.18%, because 18 is 21.18% of 85.
Percent change needs an old value and a new value. From 80 to 100, the change is (100 − 80) / 80 × 100 = 25% increase. From 100 to 80, it is (80 − 100) / 100 × 100 = −20%, a 20% decrease. The base is the old number, so a rise and the reverse fall are not the same percent.
Worked percentage examples
25 is what percent of 200?
Part 25, whole 200. The ratio is 25 / 200 = 0.125, and 0.125 × 100 = 12.5. The calculator shows 12.5%, and the detail line reads "25 is 12.5% of 200."
The same relationship backwards is "12.5% of 200 is 25," which is the percent-of formula, not a second mode of this form. Both sentences describe one ratio.
Scores, thirds, and results over 100%
A score of 45 out of 60: 45 / 60 × 100 = 75. The calculator shows 75%. Two out of three: 2 / 3 × 100 = 66.666…, shown as 66.67%. The hidden repeating 6 is rounded, not truncated to 66.66.
150 out of 80: 150 / 80 × 100 = 187.5. The calculator shows 187.5%. A result above 100% is correct whenever the part is larger than the whole. It is not an error message.
The two questions this button does not answer
What is 18% of 85? Compute 85 × 18 / 100 = 15.3 by hand. Entering 18 and 85 in this form instead produces about 21.18%, which is the share 18 represents of 85, not 18 percent of 85.
What is the percent change from 80 to 100? Compute (100 − 80) / 80 × 100 = 25, a 25% increase. The reverse, from 100 down to 80, is a 20% decrease because the base is now 100. This form has no "old" and "new" fields, so it cannot apply that formula for you.
Common percents of 200
| Part | Whole | This calculator shows | Same fact, other wording |
|---|---|---|---|
| 20 | 200 | 10% | 10% of 200 is 20 |
| 25 | 200 | 12.5% | 12.5% of 200 is 25 |
| 50 | 200 | 25% | 25% of 200 is 50 |
| 100 | 200 | 50% | 50% of 200 is 100 |
| 150 | 200 | 75% | 75% of 200 is 150 |
| 200 | 200 | 100% | 100% of 200 is 200 |
Where a two-number percent stops
The calculator does not convert a fraction in lowest terms, and it does not show repeating decimals beyond two places. 66.67% is not exactly two thirds. If you need an exact fraction, keep the division as 2/3 rather than the rounded percent.
Percent change, percent of a number, percentage points, and "percent greater than" are easy to mix up. A move from 10% to 15% is a rise of 5 percentage points, and it is also a 50% increase relative to 10. This form will not choose the interpretation. You have to know which number is the part and which is the whole.
A whole of zero cannot be used. There is no percent that expresses a part of nothing. Leave the field blank or enter 0 and the division does not produce a usable ratio.
Frequently asked questions
How do I find what percent one number is of another?
Put the first number in Part and the second in Whole. The calculator divides part by whole and multiplies by 100. Part 25 and whole 200 produce 12.5%.
Can the percentage be more than 100%?
Yes. If the part is larger than the whole, the result is above 100%. Part 150 and whole 80 produce 187.5%. That is the correct ratio, not a cap.
What happens if the whole is zero?
The percent is undefined. Dividing by zero does not produce a meaningful ratio, so the whole has to be a non-zero number.
How is percent change different from this calculator?
Percent change is (new − old) / old × 100. From 80 to 100 that is a 25% increase. This form has no old and new fields. It only computes part / whole × 100.
How do I calculate a percent of a number instead?
Multiply the number by the percent and divide by 100. Eighteen percent of 85 is 85 × 18 / 100 = 15.3. Entering 18 and 85 here answers a different question: 18 is about 21.18% of 85.