Ratio Calculator
Reduce a ratio to its simplest form, solve for a missing value in a proportion, and split a total by ratio.
12 : 18 simplifies to
2 : 3
Simplest whole-number form
Decimal form
0.6667
Common divisor
6
- Original ratio
- 12 : 18
- Greatest common divisor
- 6
- Simplified ratio
- 2 : 3
- A as a share of the total
- 40%
- B as a share of the total
- 60%
How this was calculated
- 1.Find the greatest common divisor of 12 and 18: 6.
- 2.Divide both sides: 12 ÷ 6 : 18 ÷ 6.
- 3.Simplified ratio = 2 : 3.
How the ratio calculation works
A ratio compares two quantities. Simplifying it divides both sides by their greatest common divisor, which keeps the relationship identical while making the numbers smaller.
A proportion states that two ratios are equal. Cross-multiplying turns it into a simple equation — a : b = c : x becomes a × x = b × c — which is how the missing value is found.
Splitting a total by ratio means dividing it into equal parts and handing the right number of parts to each party. Adding the ratio parts first gives you how many equal slices there are.
Worked example
Split 500 in the ratio 2:3.
- →2 + 3 = 5 parts
- →One part = 500 ÷ 5 = 100
- →A = 2 × 100, B = 3 × 100
Answer: 200 and 300.
Ratio FAQs
What is the difference between a ratio and a fraction?
A ratio compares parts of a whole to each other (2:3), while a fraction compares one part to the whole (2/5). Both describe the same split.
Can ratios have decimals?
Yes, but they are usually scaled to whole numbers. Decimal ratios are common in maps, where 1:25,000 means one unit on the map equals 25,000 on the ground.
How do I split three ways?
Add all three parts together, divide the total by that sum, then multiply by each part. This tool handles two parts; for three, the same arithmetic applies.
Ratio Calculator is part of the math calculators collection on Calcora, alongside 7 other tools. Results are calculated in your browser and are for information only — see our disclaimer.
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