Percentage Calculator

Calculate percentages, percentage change, and percentage difference.

Percentage (%)

Of number

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How it works

Three independent modes cover the most common percent questions. Mode 1 ("X% of Y") multiplies Y by X/100 — useful for tips, tax, and discounts. Mode 2 ("X is what % of Y") divides X by Y and multiplies by 100 — useful for grade-to-percentage conversion or completion ratios. Mode 3 ("change from X to Y") subtracts old from new, divides by old, then multiplies by 100 — the standard formula for growth rates and price changes.


              // Mode 1:  result = (X / 100) × Y
// Mode 2:  result = (X / Y) × 100
// Mode 3:  result = ((Y − X) / X) × 100

Common use cases

Calculating sale discounts: 25% off $80 → $20 saved, $60 final.
Converting test scores: 42 out of 50 → 84%.
Measuring growth: revenue went from $100k to $150k → +50% YoY.

See also: Salary Calculator , Loan Calculator .

Frequently asked questions

Why does Mode 3 (change) give a negative number sometimes?

Negative means a decrease. Going from 100 to 75 is −25% (a 25% drop); going from 75 to 100 is +33.3% (an increase). The asymmetry is correct — increases and decreases are not symmetric in percent terms.

How do I calculate a tip?

Use Mode 1: "What is 18% of $42?" → $7.56. Add to bill total or use the salary calculator if splitting hourly rates.

Can I divide by zero?

No — Mode 2 and Mode 3 require the denominator to be non-zero. The tool returns an error message instead of NaN or infinity.

Embed this tool

Add this free percentage calculator to your own website or blog — copy the code below and paste it into your page HTML. No signup, no API key.

<iframe src="https://otoolrun.com/embed/percentage-calculator/" width="100%" height="560" style="border:0;border-radius:12px" loading="lazy" title="Percentage Calculator"></iframe>
<p style="font-size:14px"><a href="https://otoolrun.com/tools/percentage-calculator/">Percentage Calculator by oToolRun</a></p>

💯 Percentage Calculator