Math
Ratio Simplifier
Type a ratio such as 12:18 or 2.5:7.5:10 and get it in lowest terms with the GCF shown, each part as a fraction and percent of the total, and the n:1 form.
Switch to scale mode to grow or shrink the ratio so one part equals a target amount. The two-part ratio calculator on mathcheck covers the basics; this page handles up to six parts and scaling.
Separate parts with colons, spaces, or commas. Two to six parts; decimals allowed.
Try an example
Result
Ratio
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- Simplest form
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- As fractions of the whole
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- As percents of the whole
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- n:1 form
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- Total parts
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Grade planning, algebra checks, and formulas students reach for most.
Study path
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Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
Simplifying a ratio
A ratio compares quantities by their relative size, so dividing every part by the same number keeps the comparison the same. Find the The largest number that divides evenly into every number in a set. of all the parts and divide each by it. 12:18:30 has GCF 6, so it simplifies to 2:3:5. Decimal ratios are cleared first by multiplying every part by a power of 10: 2.5:7.5 becomes 25:75 = 1:3.
Ratio parts as fractions and percents
Add the simplified parts to get the total, then each part over the total is its fraction of the whole. For 2:3:5 the total is 10, so the parts are 2/10 = 1/5 (20%), 3/10 (30%), and 5/10 = 1/2 (50%). This is how you split an amount in a given ratio: multiply the amount by each fraction.
Scaling a ratio
To scale a recipe, map, or mixture, decide what one part must become and multiply every part by the same factor. If a 2:3:5 mix needs 20 of the first ingredient, the multiplier is 20 ÷ 2 = 10 and the mix becomes 20:30:50.
| Ratio | GCF | Simplified | As percents |
|---|---|---|---|
| 12:18 | 6 | 2:3 | 40% : 60% |
| 12:18:30 | 6 | 2:3:5 | 20% : 30% : 50% |
| 2.5:7.5 | clear decimals → 25:75, GCF 25 | 1:3 | 25% : 75% |
| 0:4 | 4 | 0:1 | 0% : 100% |
How to use it
- Type the ratio with colons between the parts (12:18:30). Spaces or commas work too.
- Read the simplified ratio, the GCF used, and each part as a fraction and percent of the whole.
- For scaling, choose Scale the ratio, pick which part to fix, and enter its target value.
- Use the n:1 form when you need one part expressed per single unit of the other.
How to read the answer
The simplified ratio keeps the same comparison with the smallest whole numbers. The fractions and percents tell how much of the total each part is, which is what you need to divide money, ingredients, or time in that ratio. In scale mode the multiplier is the factor every part was multiplied by.
Common mistakes and edge cases
- Subtracting the same number from each part changes the ratio; only multiply or divide.
- Order matters: 2:3 is not the same as 3:2.
- A ratio of all zeros has no meaning, but a single 0 part is fine (0:1).
- Convert units to match before writing the ratio: 30 minutes to 2 hours is 30:120 = 1:4, not 30:2.
- Ratios compare parts to parts; fractions of the whole compare a part to the total. 2:3 means 2/5 and 3/5 of the whole.
Worked examples
Three parts
12:18:30
Ratio
2:3:5
Two parts
12:18
Ratio
2:3
Decimals
2.5:7.5
Ratio
1:3
Already simplest
7:11
Ratio
7:11
Zero part
0:4
Ratio
0:1
Scale a recipe
2:3:5 with first part 20
Ratio
20:30:50
Scale with a fractional multiplier
4:6 with second part 9
Ratio
6:9
All zeros
0:0 is undefined
Ratio
Error
Frequently asked questions
How do you simplify a ratio with three numbers?+
Find the greatest common factor of all three and divide each by it. 12:18:30 has GCF 6, so it becomes 2:3:5.
Can a ratio have decimals?+
Yes. Multiply every part by 10, 100, or 1000 to clear the decimals, then simplify: 2.5:7.5 = 25:75 = 1:3.
How do you turn a ratio into fractions?+
Add the parts for the total and put each part over it. 2:3 has total 5, so the parts are 2/5 and 3/5 of the whole.
How do you turn a ratio into percents?+
Convert each fraction of the whole to a percent. 2:3 gives 2/5 = 40% and 3/5 = 60%.
How do I scale a ratio?+
Divide the target by the current value of that part to get the multiplier, then multiply every part by it. 2:3:5 with the first part set to 20 uses multiplier 10: 20:30:50.
What does the n:1 form mean?+
The ratio written so the second part is exactly 1. 2:3 becomes 0.6667:1, which is handy for comparing ratios with different sizes.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- September 4, 2026
Method
- Uses the values entered by the user and stable formulas documented on the page.
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Last updated: September 4, 2026