Ratio to Decimal Calculator

What is a ratio to decimal calculator?

A ratio to decimal calculator turns a ratio written in the form $a:b$ into a single decimal number. A ratio compares two quantities, and dividing the first quantity by the second gives an equivalent decimal that is often easier to read, compare, and use in further calculations. Enter the two terms of the ratio and the calculator returns the decimal result instantly.

This is useful whenever you need a ratio expressed as a plain number, for example when scaling a recipe, comparing odds, working out aspect ratios, or feeding a value into a spreadsheet.

How does it work?

A ratio $a:b$ is equivalent to the fraction $\frac{a}{b}$, so converting it to a decimal is simply a matter of division:

$\text{decimal} = \frac{a}{b}$

Here $a$ is the antecedent (the first term) and $b$ is the consequent (the second term). The consequent cannot be zero, because division by zero is undefined. The calculator rounds the answer to six decimal places.

Worked examples

• The ratio $3:4$ becomes $\frac{3}{4} = 0.75$.
• The ratio $1:2$ becomes $\frac{1}{2} = 0.5$.
• The ratio $5:2$ becomes $\frac{5}{2} = 2.5$, a value greater than one because the first term is larger than the second.
• The ratio $1:3$ becomes $\frac{1}{3} = 0.333333$ (rounded to six decimal places), a repeating decimal.

Practical notes

When the antecedent is smaller than the consequent the decimal is less than one; when it is larger the decimal is greater than one; and when the two terms are equal the decimal is exactly one. Some ratios such as $1:3$ produce repeating decimals that never terminate, so the displayed value is a rounded approximation.

If you instead want to keep the result in fraction form, use the ratio to fraction calculator, and to go the other way and rebuild a ratio from a decimal, see the decimal to ratio calculator. The closely related fraction to decimal calculator performs the same division when your input is already written as a fraction.

Frequently asked questions

What does the ratio order mean? The order matters: $3:4$ divides 3 by 4, while $4:3$ divides 4 by 3, giving different decimals.

Why is there no result when the second term is zero? Dividing by zero is undefined, so the calculator leaves the result blank until you enter a non-zero consequent.

Can the terms be decimals themselves? Yes. A ratio like $1.5:0.5$ is valid and converts to $3$.