Free Percentage Calculator

How to Calculate Percentages

A percentage expresses a number as a fraction of 100. Percentages are used everywhere: shopping discounts, tax rates, exam grades, interest rates, and statistics.

Percentage Formulas

Finding a Percentage of a Number

To find X% of Y, multiply Y by X and divide by 100.

Result = Y × (X / 100)

What Percentage One Number Is of Another

Divide A by B and multiply by 100.

Percentage = (Part / Whole) × 100

Percentage Increase or Decrease

% Change = ((New − Old) / Old) × 100

Calculating a Discount

Sale Price = Original × (1 − Discount / 100)

Reversing a Percentage

Original = Result / (Percentage / 100)

Quick Reference Table

%	of 50	of 100	of 200	of 500	of 1000
5%	2.5	5	10	25	50
10%	5	10	20	50	100
15%	7.5	15	30	75	150
20%	10	20	40	100	200
25%	12.5	25	50	125	250
50%	25	50	100	250	500

Mental Math Tricks

Finding 10% of any number: move the decimal one place left. 5% is half of 10%, 20% is double 10%.

X% of Y always equals Y% of X. So 8% of 50 = 50% of 8 = 4.

Frequently Asked Questions

How do I calculate a percentage of a number?

Multiply the number by the percentage divided by 100. Example: 20% of 150 = 150 × 0.20 = 30.

How do I calculate percentage increase?

((New - Old) / Old) × 100. Example: 50 to 75 = 50% increase.

How do I calculate percentage decrease?

((Old - New) / Old) × 100. Example: 200 to 150 = 25% decrease.

How do I find the original price before a discount?

Divide sale price by (1 - discount rate). $80 after 20% off = $80 / 0.80 = $100.

How do I reverse a percentage?

Whole = Part / (Percentage / 100). If 30 is 25% of a number: 30 / 0.25 = 120.

What is X% of Y?

X is what % of Y?

Percentage Increase / Decrease

Discount Calculator

Find the Original Number (Reverse %)