Percentage Calculator

Calculate percentages, percentage change, increases, decreases, and more. Instant results as you type.

📊 What is X% of Y?

What is % of
Result
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🔢 X is what % of Y?

is what % of
Percentage
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Formula:
(X ÷ Y) × 100 = Percentage

📈 Percentage Change

From to
Change
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Formula:
((New - Old) ÷ Old) × 100

⬆️ Increase by Percentage

Increase by %
New Value
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⬇️ Decrease by Percentage

Decrease by %
New Value
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↔️ Percentage Difference

Between and
Difference
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Formula:
|V1 - V2| ÷ ((V1 + V2) ÷ 2) × 100

📜 Calculation History

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How to Calculate Percentages

A percentage is a way of expressing a number as a fraction of 100. The word itself comes from the Latin per centum, meaning "by the hundred." Percentages are used everywhere in daily life — from calculating sales tax and restaurant tips to understanding interest rates, exam scores, and investment returns.

Basic Percentage Formula

To find X% of a number, multiply the number by X and divide by 100:

(X ÷ 100) × Number = Result

For example, 15% of 200 = (15 ÷ 100) × 200 = 30

Percentage Increase & Decrease

To calculate a percentage increase, subtract the original value from the new value, divide the result by the original value, and multiply by 100. A percentage decrease follows the same formula — a negative result indicates a decrease. These calculations are essential for tracking price changes, salary raises, and population growth.

Percentage Change Formula

To calculate the percentage change between two values:

((New Value - Old Value) ÷ Old Value) × 100 = Percentage Change

Real-World Uses of Percentages

  • Tips: 15–20% of bill total at restaurants
  • Sales Tax: Tax rate % of purchase price varies by region
  • Discounts: Original price × (1 − discount%/100) gives the sale price
  • Interest: Principal × rate % × time (simple interest formula)
  • Grades: Correct answers ÷ total questions × 100

Common Mistakes to Avoid

One frequent error is confusing percentage points with percentages. If an interest rate rises from 5% to 7%, that is a 2 percentage point increase but a 40% relative increase. Another common mistake is applying successive percentage changes incorrectly — a 50% increase followed by a 50% decrease does not return to the original value; it results in 75% of the starting amount.

Frequently Asked Questions

Multiply the number by the percentage and divide by 100. For example, 25% of 80 = (25 × 80) ÷ 100 = 20.

Percentage change measures the relative change from an old value to a new value. Percentage difference compares two values relative to their average, without assuming one is the "original."

Multiply the number by (1 + percentage/100). For example, to add 15% to 100: 100 × 1.15 = 115.