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Percentage Calculator

Calculate percentages, percentage increase/decrease, and find what percent one number is of another. Free online percentage tool.

What Is a Percentage Calculator?

A percentage calculator is a versatile math tool that solves the most common percentage problems instantly. Percentages are used everywhere — from calculating discounts and sales tax to tracking investment returns, measuring grade scores, analyzing data changes, and computing tips at restaurants.

This calculator handles five types of percentage calculations: finding a percentage of a number (e.g., 20% of 150 = 30), determining what percent one number is of another (e.g., 30 is 20% of 150), calculating percentage change between two values (increase or decrease), and adding or subtracting a percentage from a number (useful for discounts, markups, and tax calculations).

The percentage change formula is particularly useful for business and finance: ((New − Old) / Old) × 100. A positive result means an increase; negative means a decrease. For example, if a stock price goes from $80 to $100, the percentage change is ((100 − 80) / 80) × 100 = +25%.

Each calculation shows the full formula with your numbers substituted in, so you can understand the math and verify the result manually.

Percentage Formulas

X% of Y

Result = (X / 100) × Y

20% of 150 = (20/100) × 150 = 30

X is what % of Y

Result = (X / Y) × 100

30 is what % of 150 = (30/150) × 100 = 20%

% Change

Result = ((New − Old) / Old) × 100

50 to 60 = ((60−50)/50) × 100 = +20%

Add %

Result = Number × (1 + %/100)

200 + 15% = 200 × 1.15 = 230

Subtract %

Result = Number × (1 − %/100)

200 − 20% = 200 × 0.80 = 160

Frequently Asked Questions

How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. Formula: (Percentage / 100) × Number. Example: 20% of 150 = (20 / 100) × 150 = 30.

How do I calculate percentage increase?

Formula: ((New Value − Old Value) / Old Value) × 100. Example: price increased from $50 to $60. ((60 − 50) / 50) × 100 = 20% increase.

How do I calculate percentage decrease?

Same formula as increase: ((New Value − Old Value) / Old Value) × 100. If the result is negative, it's a decrease. Example: $100 to $80 = ((80 − 100) / 100) × 100 = −20% (20% decrease).

What percent is X of Y?

Formula: (X / Y) × 100. Example: What percent is 25 of 200? (25 / 200) × 100 = 12.5%.

How do I add a percentage to a number?

Multiply the number by (1 + percentage/100). Example: Add 15% to 200 = 200 × 1.15 = 230. Or calculate the increase (200 × 0.15 = 30) and add it (200 + 30 = 230).

How do I subtract a percentage from a number?

Multiply the number by (1 − percentage/100). Example: Subtract 20% from 150 = 150 × 0.80 = 120. This is commonly used for calculating discounts.

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