Ratio Calculator
Simplify a ratio to its lowest terms and compute the decimal ratio, or scale a ratio to a target value.
This free online ratio calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
Minimum: 0.0001
Results
Simplified A
3
Simplified B
2
Decimal Ratio (A/B)
1.5
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Ratio Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Ratio Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
When to Use This Calculator
- •Use the Ratio Calculator when you need a quick mathematical result without writing out all the steps manually, saving time on repetitive calculations.
- •Use it to verify hand calculations on tests or assignments and catch arithmetic mistakes.
- •Use it when teaching or explaining mathematical concepts to others, demonstrating how changing inputs affects the result.
- •Use it to explore the behavior of mathematical functions across a range of inputs.
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About Ratio Calculator
A ratio expresses the relative size of two or more quantities. Ratios appear everywhere: screen aspect ratios (16:9), mixing ratios in chemistry, gear ratios in engineering, and financial ratios in accounting. This calculator simplifies a ratio to its lowest terms by dividing both values by their greatest common divisor, similar to simplifying a fraction. It also computes the decimal equivalent for easy comparison. Simplified ratios are cleaner and easier to communicate. Understanding ratios builds the foundation for proportional reasoning, scaling, and many applications in science and business.
The Math Behind It
Formula Reference
Ratio Simplification
a : b = (a/GCD) : (b/GCD)
Variables: a, b = ratio values, GCD = greatest common divisor of a and b
Worked Examples
Example 1: Simplifying a ratio
Simplify 12:8
12:8 = 3:2 (decimal 1.5)
Common Mistakes & Tips
- !Not simplifying to the lowest terms.
- !Reversing the order of the ratio, which changes its meaning.
- !Confusing ratios with fractions in context (a ratio of 3:2 means 3 parts to 2 parts, not 3/2 of a whole).
- !Applying ratio simplification to part-to-whole when it should be part-to-part or vice versa.
Related Concepts
Used in These Calculators
Calculators that build on or apply the concepts from this page:
Frequently Asked Questions
Is a ratio the same as a fraction?
They are related but used differently. A fraction represents a part of a whole; a ratio compares two separate quantities. Mathematically, they can be treated similarly for simplification.
Can a ratio have decimals?
Typically ratios use whole numbers. If you have a decimal ratio like 2.5:1, multiply both by 2 to get 5:2.
What is an aspect ratio?
An aspect ratio describes the proportional relationship between width and height, such as 16:9 for widescreen displays.
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