How to Convert Percentages to Decimals

While the calculator above gives you an instant answer with a step-by-step breakdown, understanding the math behind the conversion is essential for students, financial analysis, and coding.

A percentage is simply a ratio that represents a part of a whole, specifically “per 100.” The word comes from the Latin per centum, literally meaning “by the hundred.”

Converting a percentage to a decimal converts that relative ratio into an absolute number (a multiplier) that you can use in equations.

The Core Formula

Formula:

Decimal = Percent / 100

Example 1: Whole Numbers

Let’s say you have 45%.

45 ÷ 100 = 0.45.

Example 2: Small Percentages

If you have a fractional percentage, like 0.5% (half a percent).

0.5 ÷ 100 = 0.005

Example 3: Greater than 100%

Percentages larger than 100 result in decimals greater than 1. For example, 250%.

250 ÷ 100 = 2.5.

The “Two-Step” Shortcut (Moving the Decimal)

Here is how to do it manually:

1. Locate the decimal point. If the number is a whole number (like 75%), the decimal is invisible but sits at the end (75.).
2. Move it two jumps left.
3. Fill empty gaps with zeros. If you run out of numbers while moving left, place a 0 as a placeholder.
4. Drop the symbol. Remove the %.

Why do we calculate this?

• Calculating Sales Tax: If tax is 8%, you cannot multiply your price by “8.” You multiply by 0.08.
• Finding Discounts: To find 20% off a $50 shirt, you multiply $50 × 0.20.
• Banking & Interest: An interest rate of 3.5% APY is used in compound interest formulas as 0.035.

Conversion Chart

Percent	Decimal	Fraction
1%	0.01	1/100
5%	0.05	1/20
10%	0.1	1/10
12.5%	0.125	1/8
20%	0.2	1/5
25%	0.25	1/4
33.33%	0.333…	1/3
50%	0.5	1/2
75%	0.75	3/4
90%	0.9	9/10
100%	1.0	1
150%	1.5	3/2

FAQs

Q1. How do I convert a decimal back to a percentage?

A: Reversing the process is just as easy. Multiply the decimal by 100 and add the “%” sign.

• 0.65 × 100 = 65%
• 1.25 × 100 = 125%

Q2. What happens if I have a percentage like 0.001%?

A: The rule remains the same. Move the decimal two places left. 0.001% becomes 0.00001. These microscopic numbers are often used in science (probability) and high-frequency trading.

Q3. Why does 100% equal 1?

A: 100% represents the “whole” amount. If you have 100% of a pizza, you have 1 entire pizza. Therefore, mathematically, 100% is equal to the integer 1.

Sources: CalculatorSoup, Inch Calculator, RapidTables, CalculateStuff, Vedantu, GigaCalculator, beGalileo, eMathHelp, Calculator-Online, GeeksforGeeks.