Percent of versus percent off
“15% of 200” is 30. “15% off 200” is 170. The third mode (X is Y% of what) solves for the original. Pick the question that matches the sentence you are trying to finish.
Your numbers
Percentage
Common percent operations and discounts. Each stays a separate calculation.%
Result
30How we got this
- Operation15% of 200
- Result30
What we assumed
- Percent of: (percent ÷ 100) × base.
- What percent: part ÷ whole × 100. A zero whole is rejected.
- Percent of what: part ÷ (percent ÷ 100). A zero percent is rejected.
- Percent off: discount cannot exceed 100%.
Technical details
Method percentage-v1.0.0Data Manual inputs / fixed rules
Discrepancy in the numbers? You can click Report incorrect result below or email hello@costanswer.com with the Method and Data lines.
Guide
Three percent questions, exactly
What is X% of Y, X is what percent of Y, and X is Y% of what. Division by zero is rejected. This is not a mortgage rate and not a tax bracket.
Questions about this calculator
What is 15 percent of 200?
30, using the first mode. A sale price of 15% off 200 is a different question; use the wording on the page that matches “off.”
How do I find what percent 40 is of 200?
Use the “X is what percent of Y” mode: 40 ÷ 200 × 100 = 20%. The page does that arithmetic exactly.
Terms used here
- Percent
- A ratio times 100. This page does not add tax or round to currency unless the display does.
Practical tips
For a price change from old to new, the percent-change calculator is the clearer tool.
Limits and caveats
Exact arithmetic for the mode you picked. Not financial advice.
Results are for information. They are not legal, tax, medical, or financial advice. How the math is maintained · Report a wrong figure.
Engine notes
Rounding, versioning, and omissions that sit beside the guide rather than repeating it.
- X% of Y. Result = (X ÷ 100) × Y. Example: 15% of 200 is 30.
- X is what percent of Y. Result = (X ÷ Y) × 100. A zero baseline is rejected instead of returning Infinity.
- X is Y% of what. Result = X ÷ (Y ÷ 100). A zero percent cannot solve for the missing base.