Percent Of Calculator

Calculate X% of Y with step-by-step explanation and real-world examples.

Calculate

Percentage (%)

Number

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Formula

result = (percentage / 100) × number

Example

percentage:20

number:500

result:100

Complete Guide

Reviewed by PercentLab Editorial Team · Last updated: 2026-09-07

A percent of calculator answers the first of three percentage questions: what is X% of Y? The formula is result = (percentage / 100) x number — 20% of 500 is 0.20 x 500 = 100. The other two questions (Y is what % of X, and Y is P% of what) use the same numbers rearranged, and confusing them is the most common error on this page.

For mental math, anchor everything on 10%: move the decimal one place left (10% of 250 = 25). From there, 5% is half of 10%, 20% is double, 25% is divide by 4, and 50% is divide by 2. Five anchors cover nearly every everyday calculation without a calculator.

This page is the hub of the percentage family: discounts take a slice off, sales tax adds one on, and percentage increase compares two values. Use the worked examples below, then follow the related calculators for your exact question.

Worked examples

Basic: 20% of 500

Convert the percent to a decimal: 20 / 100 = 0.20.
Multiply: 0.20 x 500 = 100.

20% of 500 is 100.

Reverse: 30 is what % of 120

Divide part by whole: 30 / 120 = 0.25.
Multiply by 100: 0.25 x 100 = 25%.

30 is 25% of 120.

Find the whole: 45 is 30% of what

Divide the part by the decimal: 45 / 0.30.
Result: 150.
Check: 0.30 x 150 = 45.

The whole is 150.

Mental shortcuts that always work (shown on $200).

Shortcut	Math	On $200
10% — move decimal	200 → 20.0	$20
5% — half of 10%	20 / 2	$10
20% — double 10%	20 x 2	$40
25% — divide by 4	200 / 4	$50
50% — divide by 2	200 / 2	$100

Mistakes to avoid

Confusing % of with % more than

20% of 100 is 20; 20% more than 100 is 120. One slices, one grows — different calculators.

Forgetting to divide by 100

20 x 500 = 10,000 is not 20% of anything. Always convert the percent to a decimal first.

Misplacing the decimal on small percents

0.5% of 200 is 1, not 10: 0.5 / 100 = 0.005, and 0.005 x 200 = 1.

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Frequently Asked Questions

To calculate 20% of 500, divide 20 by 100 to get 0.20, then multiply by 500: (20 ÷ 100) × 500 = 0.20 × 500 = 100. So 20% of 500 is 100.

The formula is: Result = (Percentage ÷ 100) × Number. For example, to find 15% of 200: (15 ÷ 100) × 200 = 30.

Yes, percentages can exceed 100%. For example, 150% of 100 is (150 ÷ 100) × 100 = 150.

20% of 100 is 20. 20% more than 100 is 100 + 20 = 120. One takes a slice, the other grows the whole — see our percentage increase calculator for the second.

Anchor on 10% (move the decimal left: 10% of 250 = 25), then build: 5% is half of 10%, 20% is double, 25% is divide by 4, 50% is divide by 2.