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How do I calculate percentages?

Calculate percentages, percentage changes, and percentage differences. Find what percent one number is of another.

What This Calculator Is

A percentage calculator solves common percentage problems: finding what percent one number is of another, calculating a percentage of a number, and determining percentage increase or decrease. It handles the mental math that trips most people up, providing accurate results instantly.

Who This Calculator Is For

Students learning percentage concepts, shoppers calculating discounts, workers computing tips or commission, and anyone who encounters percentage problems in daily life. It's a universal math helper for a universally confusing topic.

When to Use This Calculator

Use this calculator when shopping and comparing discounts, calculating tips, figuring out test scores or grades, determining percentage changes in data, or whenever you need quick and accurate percentage calculations.

Inputs

Value 1

Value 2

100

Percentage

25.000%

Results

Value 1 is % of Value 2

25.000%

% Change (V1 to V2)300.000%

Percentage of Value 225

Difference75

Results are for informational purposes. Verify calculations for critical applications.

Insights

Quick reference

25.00 is 25% of 100. 25 is 25.00% of 100.

How Percentage Is Calculated

Percentage = (Part / Whole) × 100. Percentage change = ((New - Old) / Old) × 100. To find X% of a number, multiply the number by X/100.

percentOf = (value1/value2)*100
percentChange = ((value2-value1)/|value1|)*100
valueFromPercent = value2*(percentageValue/100)
difference = value2 - value1
Where:
value1, value2, percentageValue are independent user inputs (defaults 25, 100, 50)
Assumptions:
percentChange uses absolute value of value1 in the denominator (so result sign reflects direction even if value1 is negative)
Division-by-zero guarded by returning 0 instead of Infinity/NaN

Key Takeaways

•To find what percent A is of B: (A ÷ B) × 100
•To calculate a percentage increase: ((New - Old) ÷ Old) × 100
•To find X% of a number: Number × (X ÷ 100)
•A 50% increase followed by a 50% decrease does NOT return to the original value
•Percentage points ≠ percent change (5% to 10% is 5 percentage points but a 100% increase)

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