About the Ratio Calculator
This ratio calculator handles the three things people most often need to do with a ratio. Simplify reduces a ratio such as 1920 : 1080 or 2.5 : 7.5 to its smallest whole-number form (16 : 9 and 1 : 3). Solve finds the missing fourth term in a proportion A : B = C : ?, which is how you scale a recipe, a map distance or a mixing instruction. Scale multiplies both sides of the ratio by the same factor.
Every mode also shows the ratio as a single number (A ÷ B), as a "1 : n" unit ratio, and as a percentage split of the whole — useful for dividing money, shares or ingredients between two parts. The pie chart makes the split easy to see at a glance.
Ratios compare quantities of the same kind, so make sure both parts use the same unit (both in grams, or both in millilitres) before you simplify or solve.
How to use the ratio calculator
- 1Choose Simplify, Solve or Scale.
- 2Enter the two terms of your ratio, A and B, in the same unit.
- 3For Solve, enter the known term C of the new ratio; for Scale, enter the factor.
- 4Read the result, the simplest form and the percentage split.
Formula and method
To simplify, the calculator first turns any decimals into whole numbers by multiplying both terms by the same power of ten, then divides both by their greatest common divisor. Multiplying or dividing both sides of a ratio by the same non-zero number never changes it, which is also why scaling works.
To solve a proportion, write both ratios as fractions and cross-multiply: A × D = B × C, so the missing term D = B × C ÷ A. The percentage split treats A + B as the whole, so A’s share is A ÷ (A + B) × 100.
- A, B
- The two terms of the original ratio
- C, D
- The terms of the equivalent ratio (D unknown)
- g
- Greatest common divisor of A and B
Worked examples
Simplify 1920 : 1080 (screen resolution)
The greatest common divisor of 1920 and 1080 is 120. Dividing both by 120 gives 16 : 9, the standard widescreen aspect ratio. A makes up 1920 ÷ 3000 = 64% of the total.
Scale a 16 : 9 screen to 1280 wide
Cross-multiplying, the missing height = 9 × 1280 ÷ 16 = 720, so a 16 : 9 image 1280 pixels wide is 720 pixels tall.
Simplify a decimal ratio 2.5 : 7.5
Multiply both terms by 10 to get 25 : 75, then divide by the GCD of 25 to get 1 : 3. A is one quarter (25%) of the whole.
Triple a 2 : 3 mixing ratio
Multiplying both parts by 3 turns 2 : 3 into 6 : 9 — for example 6 cups of flour to 9 cups of water — while keeping exactly the same proportions.
Frequently asked questions
How do you simplify a ratio?+
Divide both terms by their greatest common factor. For 18 : 24 the GCF is 6, so the ratio simplifies to 3 : 4. If there are decimals, first multiply both terms by 10, 100 and so on to make them whole numbers.
How do I solve a ratio for x?+
Write it as a proportion and cross-multiply. For 3 : 5 = 12 : x, compute 3x = 5 × 12 = 60, so x = 20. This calculator does the same with D = B × C ÷ A.
How do I split an amount in a given ratio?+
Add the parts to get the total number of shares, divide the amount by that total, then multiply by each part. To split $500 in the ratio 2 : 3, one share is $100, so the parts are $200 and $300.
What is the difference between a ratio and a fraction?+
A ratio compares one part with another (2 : 3), while a fraction compares a part with the whole (2/5). The ratio 2 : 3 means the first part is 2/5 of the total and the second is 3/5.
Can a ratio have more than two parts?+
Yes — concrete mixes such as 1 : 2 : 3 compare three quantities. The same rules apply: divide all parts by their common factor to simplify, and multiply all parts by the same number to scale.