Ratio Calculator
Reduce a ratio of two parts to lowest terms, show each part as a percentage, and split a total in that ratio, with an 8:12 worked example.
Results
Simplified ratio
- A as % of total
- 40%
- A share of total
- 40
- B share of total
- 60
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Formula / how it works
Simplified ratio = a ÷ GCF : b ÷ GCF. Share of total for A = a ÷ (a + b) × total; for B = b ÷ (a + b) × total.
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
A ratio compares two quantities. 8:12 says that for every 8 of one thing there are 12 of another, and it simplifies to 2:3 because both parts divide by 4. Ratios appear in recipes, mixing instructions, scale models, finance and sharing costs. This calculator simplifies a two-part ratio and, if you supply a total, splits that total in the same proportion and shows the percentage for part A. It is for two-part ratios; for three or more parts, simplify them all by their common factor and divide the total by the sum of the parts. Ratios are unitless, so both parts must be in the same unit.
When to use / who it helps
- You want to reduce a ratio to simplest form.
- You need to divide an amount in a given ratio.
- You are scaling a recipe or mixture.
- You are checking a map or model scale.
- You want to express a ratio as percentages.
How to use
Steps
- Enter part A.
- Enter part B.
- Enter a total to share, or leave it at zero to skip.
- Read the simplified ratio.
- Read each part's share of the total.
- Check that the shares add up to the total.
How to interpret results
- The simplified ratio is the smallest whole-number form.
- Percentages show each part as a share of the sum.
- Shares add up to the total you entered.
- A ratio like 2:3 means 2 parts out of 5 in total.
- Both parts must use the same unit.
Common mistakes & gotchas
- Treating 2:3 as 2 out of 3 instead of 2 out of 5.
- Mixing units in the two parts.
- Reversing the order of the parts.
- Entering a total of zero and expecting shares.
- Forgetting to simplify.
Worked example
Worked example — 8:12 shared across 100
- The GCF of 8 and 12 is 4, so 8:12 simplifies to 2:3.
- Total parts: 2 + 3 = 5, so A is 2 ÷ 5 = 40%.
- A's share of 100: 40; B's share: 60.
- For a total of 25: A gets 25 × 2 ÷ 5 = 10 and B gets 15.
Result: 8:12 simplifies to 2:3, which splits 100 into 40 and 60.
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
Simplified ratio = a ÷ GCF : b ÷ GCF. Share of total for A = a ÷ (a + b) × total; for B = b ÷ (a + b) × total.
Frequently asked questions
How do I simplify a ratio?
Divide both parts by their greatest common factor.
How do I share an amount in a ratio?
Divide it by the sum of the parts and multiply by each part.
What does 2:3 mean as a fraction?
Part A is 2/5 of the total and part B is 3/5.
Can I use decimals?
Convert them to whole numbers by scaling first.
What is the difference between a ratio and a fraction?
A ratio compares parts to each other; a fraction compares a part to the whole.
How do I handle three parts?
Divide the total by the sum of all three parts.