Ratio Calculator

Ratios describe how quantities share a whole: recipe ingredients, map scales, screen aspect ratios, investment splits. This ratio calculator simplifies any two-term ratio to its lowest form, shows each side’s percentage share, and can split a total amount according to the ratio.

Enter 24 and 36 and it reduces to 2:3; add a total of 500 and it splits it into 200 and 300.

Enter valid values to see the results.

Formula

Simplified ratio = A ÷ gcd(A, B) : B ÷ gcd(A, B). Share of total = Total × A ÷ (A + B)

The greatest common divisor (gcd) is the largest number dividing both terms evenly. Dividing both terms by it preserves the proportion while giving the smallest whole-number form.

What you need

Enter the two terms of the ratio in any units — only their relationship matters.
The optional total splits any amount (money, ingredients, votes) in the same proportion.
Decimals are fine: 1.5 : 2.5 simplifies to 3 : 5.

Worked example

A concrete mix of 24 kg cement to 36 kg sand: gcd(24, 36) = 12, so the ratio simplifies to 2:3. Cement is 24 ÷ 60 = 40% of the mix. To make 100 kg total: 40 kg cement and 60 kg sand.

Practical tips

A ratio and a fraction are the same idea: A:B as a fraction is A ÷ (A + B) of the whole.
To scale a recipe ratio, multiply all terms by the same factor — the proportion is preserved.
Aspect ratios work identically: 1920:1080 simplifies to 16:9.
When comparing ratios, convert to percentages or decimals first — 3:4 vs 7:9 is easier as 75% vs 77.8%.

Common ratios and their percentage shares

Ratio	Share A	Share B
1:1	50%	50%
1:2	33.3%	66.7%
2:3	40%	60%
3:4	42.9%	57.1%

Common mistakes

1 Simplifying only one term — both must be divided by the same divisor.
2 Reading A:B as “A out of B” — A:B means A parts per B parts, so A is A/(A+B) of the whole, not A/B.
3 Rounding intermediate values when splitting a total, leaving a remainder unallocated.

Frequently asked questions

How do I simplify a ratio?

Divide both terms by their greatest common divisor. 24:36 → divide by 12 → 2:3. If no common divisor exists, the ratio is already in lowest terms.

How do I split an amount by a ratio?

Add the terms, divide the total by that sum, then multiply by each term. Splitting $500 in 2:3: 500 ÷ 5 = 100, so $200 and $300.

Is 2:3 the same as 2/3?

Not quite: 2:3 means 2 parts against 3 parts, so the first share is 2/5 = 40% of the whole. The fraction 2/3 would be the ratio 2:1.

Can ratios have more than two terms?

Yes — 1:2:3 mortar mixes are common. The same method applies: divide all terms by their common divisor, and shares use the sum of all terms.