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Percentage Calculator

One card, three practical percent formulas: X% of Y, X is what % of Y, and X is Y% of what. Each mini-tool uses BigNumber-safe math via core-engine.js.

3-in-1 Percentage Tools

Tool A: What is [X]% of [Y]?

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Enter values and click Calculate.

Tool B: [X] is what percentage of [Y]?

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Enter values and click Calculate.

Tool C: [X] is [Y]% of what?

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Enter values and click Calculate.

How to Calculate Percentages Manually

A classic setup is is / of = % / 100. This proportion lets you solve unknowns by cross-multiplication instead of memorizing separate tricks for every percent question.

  • Set up the proportion with your known values: is / of = % / 100.
  • Cross-multiply to clear the fractions: is × 100 = of × %.
  • Isolate the unknown by dividing both sides by the remaining factor. This produces the same formulas used in the three tools above.

FAQ

How do I calculate 20% of a number?

Convert the percent to a decimal and multiply by the number: 20% = 0.20, so 20% of 50 is 0.20 × 50 = 10. In formula form, (x / 100) × y.

What is the formula for percentages?

A common proportion form is is/of = %/100. Rearranging gives the three practical formulas used here: (x/100)×y, (x/y)×100, and x/(y/100).

Disclaimer. RapidRatio is informational only. It is not financial, tax, business, or professional advice. Verify results and assumptions with qualified professionals before making decisions.