18 is 45% of 40.
Worked out below step by step, with a table of related values and a live calculator so you can change the numbers.
Check it: 45% of 40 = 18, which is the part you started with.
percent = (part ÷ whole) × 100
To express one number as a percentage of another, divide the part by the whole and scale it to 100.
This calculation compares the part, 18, with the whole, 40. Divide the part by the whole to get the proportion, then multiply by 100 to express that proportion as a percentage.
The answer is 45%. A result below 100% means the part is smaller than the whole; 100% means they are equal; and a result above 100% means the part is larger than the reference whole.
18:40 simplifies to 9:20. Reading that reduced ratio as a decimal and multiplying by 100 gives the same percentage, which is a useful check on the direct formula.
36 is what percent of 40?
Divide the part by the whole: 36 ÷ 40 = 0.9. Multiply by 100 to turn the decimal into a percentage. 36 is 90% of 40. This uses the same method with different numbers, so it shows how the rule transfers instead of only repeating the original answer.
The part-to-whole decimal is 0.45, and the whole-number ratio simplifies to 9:20. Multiplying the decimal ratio by 100 converts the same relationship into 45%; the percentage changes if the denominator used as the whole changes.
Part-to-whole percentages appear in test scores, completion rates, defect rates, survey results, utilisation and market shares. The denominator must represent the intended whole, because changing that reference changes the percentage meaning.
18:40 simplifies to 9:20. Reading that reduced ratio as a decimal and multiplying by 100 gives the same percentage, which is a useful check on the direct formula. Form the ratio 18 ÷ 40. 18 ÷ 40 = 0.45. 0.45 × 100 = 45%.
Reversing the part and the whole; the intended ratio here is 18 ÷ 40, not the other way around. After correcting that setup, verify the result independently: Check it: 45% of 40 = 18, which is the part you started with.
Yes. 36 is what percent of 40? Divide the part by the whole: 36 ÷ 40 = 0.9. Multiply by 100 to turn the decimal into a percentage. 36 is 90% of 40. This uses the same method with different numbers, so it shows how the rule transfers instead of only repeating the original answer. The live calculator above lets you replace both inputs and recalculate without changing the underlying method.
The part-to-whole decimal is 0.45, and the whole-number ratio simplifies to 9:20. Multiplying the decimal ratio by 100 converts the same relationship into 45%; the percentage changes if the denominator used as the whole changes. Use that scale or ratio check together with the reverse calculation before reusing the result in another calculation.
| Part | Percent of 40 |
|---|---|
| 2 | 5% |
| 4 | 10% |
| 8 | 20% |
| 10 | 25% |
| 18 | 45% |
| 20 | 50% |
| 30 | 75% |
| 40 | 100% |