Simplify a ratio
e.g. 8 : 12 reduces to 2 : 3
Scale a ratio
e.g. 2 : 3 = 6 : ? (resizing a recipe or photo)
Last updated 3 September 2026
Simplify vs scale
Simplifying takes a ratio like 8:12 and reduces it to the smallest whole numbers that describe the same relationship — 2:3. Divide both sides by their greatest common divisor and that's the answer.
Scaling answers a different question: if 2:3 stays proportional and the first number becomes 6, what does the second number become? Multiply the known ratio through: 6 ÷ 2 × 3 = 9, so 2:3 scales to 6:9. This is exactly the maths behind resizing a recipe, a photo, or a scale model while keeping the proportions correct.
Ratios, fractions and parts
The most common error with ratios is treating a part as though it were the whole. If a mix is 2:3, the 2 is not two-thirds and not 20% — there are five parts in total, so the first share is 2/5, or 40%. Getting this wrong quietly ruins concrete mixes, paint tints, cocktail recipes and profit splits alike.
Scaling is the other half of the job. A 2:3 ratio scaled to a total of 250 gives 100 and 150, found by dividing 250 by the five parts to get 50 per part, then multiplying out. Three-term ratios work identically: 1:2:2 across a 400 total is 80, 160 and 160.
A worked example
Two people fund a project 3:5 and it returns $6,400. There are eight parts, so each part is $800, and the split is $2,400 and $4,000. Notice that the second partner does not get "5% more" or "two more" — they get 62.5% of the return against 37.5%, and expressing it as percentages is often the clearest way to check a ratio has been applied correctly.
Aspect ratios are a special case worth knowing. 16:9 and 1920:1080 are the same ratio, because dividing both sides of 1920:1080 by 120 gives 16:9. Any pair of dimensions that reduces to the same simplified ratio will scale without distortion, which is exactly what you are checking when you resize an image or set a video frame.
Common questions
How do you simplify a ratio?
Divide both numbers by their greatest common divisor. 8:12 and 2:3 describe the same relationship, but 2:3 is the simplest form — the calculator finds that divisor automatically.
How does scaling a ratio work?
If A is to B as C is to an unknown, the unknown equals B × C ÷ A. This is the same maths as resizing a recipe or a photo while keeping the proportions identical.
Can a ratio have more than two numbers?
Yes, ratios like 2:3:5 are common, but this calculator handles the two-number case, which covers the large majority of everyday uses like mixing, scaling and resizing.
Does a 2:3 ratio mean 20% and 30%?
No. Add the terms to get the total number of parts — here five. The first share is 2/5, or 40%, and the second is 3/5, or 60%. Reading the ratio terms as percentages directly is the most frequent mistake made with ratios.
How do I scale a ratio to a specific total?
Divide the total by the sum of the ratio terms to get the value of one part, then multiply each term by it. For 2:3 across a total of 250, one part is 50, so the split is 100 and 150.
Are 16:9 and 1920:1080 the same ratio?
Yes. Dividing both sides of 1920:1080 by 120 gives 16:9. Any dimensions that simplify to the same ratio have the same shape, which is why an image at either size scales to the other without stretching or cropping.