Ratio Calculator
Simplify a ratio, and split an amount in that ratio.
Good to know. A 16:9 screen and a 1920 × 1080 one are the same shape. Ratios ignore size.
How it works
In plain words
Divide both parts by their greatest common divisor to simplify. To split an amount, divide it by the total number of parts, then multiply by each part.
The formula
simplified = A ÷ gcd(A, B) : B ÷ gcd(A, B) A gets = total × A ÷ (A + B) B gets = total × B ÷ (A + B)
Worked example
12 : 18 — both divide by 6, so the ratio simplifies to 2 : 3. Splitting 100 in that ratio gives 40 and 60.
Sources
No outside data or rates: this is plain arithmetic.
5 automated tests check its answers on every change.
About the ratio calculator
A ratio compares two amounts: 2 : 3 means that for every 2 of the first thing, there are 3 of the second. Ratios are everywhere, from recipes (2 parts water to 1 part rice) and paint mixing to screen aspect ratios, map scales and splitting money fairly.
Simplifying a ratio works like simplifying a fraction: divide both sides by the largest number that goes into both. 12 : 18 becomes 2 : 3, because 6 goes into both. Decimals are fine too: 1.5 : 2.5 is the same as 15 : 25, which simplifies to 3 : 5.
Splitting an amount in a ratio is one of the most practical uses. If two people invest 12,000 and 18,000 in a project and it makes a profit of 100, they share it 2 : 3. Add the parts (2 + 3 = 5), divide the amount by 5 to get the value of one part (20), and multiply: 40 and 60.
The "1 : n" form is useful for scales and dilution: 1 : 1.5 means one and a half times as much of the second thing. For scaling a recipe or a drawing to a new size, the rule of three calculator is quicker.
Questions people ask
How do I simplify a ratio?
Divide both numbers by their greatest common divisor. 12 : 18 ÷ 6 = 2 : 3.
How do I divide an amount in a ratio?
Add the parts, divide the amount by that sum, and multiply by each part. 100 in 2 : 3 is 100 ÷ 5 = 20, so 40 and 60.
Can a ratio have decimals?
Yes. The calculator scales them to whole numbers first, so 1.5 : 2.5 simplifies to 3 : 5.