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Percentage Calculator

Verified 2026-04-29 Report an error

%
Result
50.00

A percentage calculator answers the most common question in everyday math: what is X% of Y? Enter the percentage and the value — the result appears instantly. Useful for tip math, sales tax, discounts, grade calculations, and any time you need to take a slice of a number.

The formula is straightforward: (percent / 100) × value. The mental tricks in the section below make most everyday percentages doable in your head, no calculator needed.

Key takeaway

A percentage is just a fraction with 100 as the denominator. "20% of 250" really means "20 out of every 100, applied to 250" — which is the same as 0.20 × 250. Once you see the percent sign as "÷ 100," every percentage problem becomes a multiplication problem, and most of them collapse to mental shortcuts.

How it's calculated

There are three classic percentage problems, all variations of the same equation:

  • What is X% of Y? → result = X × Y ÷ 100 (this calculator)
  • X is what percent of Y? → percent = X ÷ Y × 100
  • X is Y% of what? → value = X ÷ Y × 100

Algebraically all three solve X = (percent ÷ 100) × value for whichever variable is missing. Once you internalize the structure, you don't need to memorize three formulas — you just rearrange one equation.

Source: Elementary arithmetic — percent × value ÷ 100

Quick tricks

  • 10% — move the decimal one place left. $87 → 10% is $8.70. The atomic operation behind almost every other percentage trick.
  • 5% — take 10%, then halve it. $87 → $8.70 → $4.35. Useful when 10% feels too generous and 1% too stingy.
  • 20% — take 10%, then double it. Tipping at 20%. $87 → $8.70 → $17.40.
  • 1% — move the decimal two places left. Quick scaling. 1% of $4,500 is $45. Multiply that by your target percentage.
  • Reverse the operation: 8% of 50 = 50% of 8. Whenever the calculation feels backwards. X% of Y always equals Y% of X — pick whichever is easier to do in your head.

Examples

20% of 250

20% of 250 is 50. Mental shortcut: 10% of 250 is 25, double it for 20% → 50. This is the math behind a 20% restaurant tip on a $250 dinner check.

15% of 86.40

15% of $86.40 is about $12.96. Mental shortcut: 10% is $8.64, half of that is $4.32, sum to $12.96. Useful for budgeting category percentages or estimating a 15% tip without a phone.

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage, then divide by 100. So 20% of 250 is (20 × 250) ÷ 100 = 50. Equivalently, convert the percentage to a decimal first (20% = 0.20) and multiply: 0.20 × 250 = 50. Both routes give the same answer; pick whichever feels more natural.

How do I do percentages in my head?

Anchor on 10% — moving the decimal one place left. Once you have 10%, every other percentage is a small adjustment: double it for 20%, halve it for 5%, add 1% increments (decimal moved two places) for the rest. This single anchor handles 95% of everyday percentage math without a calculator.

What's the difference between percentage and percentage points?

A percentage is a relative measure (X out of 100). Percentage points are the difference between two percentages. If a mortgage rate goes from 5% to 7%, that's a 2 percentage point increase, but a 40% percentage increase (because 7 is 40% larger than 5). Mixing these up causes a lot of confusion in news headlines about interest rates and polling.

How do I convert a fraction to a percentage?

Divide the numerator by the denominator, then multiply by 100. So 3/8 becomes 3 ÷ 8 = 0.375, times 100 = 37.5%. Easy reference points: 1/2 = 50%, 1/4 = 25%, 1/3 ≈ 33.3%, 1/5 = 20%, 1/8 = 12.5%, 1/10 = 10%.