Three-Term Ratio Calculator

How it is calculated

The tool takes three amounts A, B and C and reports their proportions. The total is T = A + B + C and each share is share = term ÷ T × 100; the total is shown with two decimals. The ratio is simplified by dividing all three terms by their greatest common divisor, g = gcd(A, B, C), but only when all three are positive whole numbers. For decimals or a zero term the ratio is shown as entered with two decimals and not reduced (1.5 : 2 : 2.5 stays 1.50 : 2.00 : 2.50), though the percentages are still correct. Negative values are rejected, and so is an all-zero input, because the total must be above zero; in those cases no result appears.

Common mistakes

• Mixing units between the three terms, such as kilograms for one and litres or shovels for another. A ratio only makes sense when all three parts are measured the same way.
• Entering decimals and expecting a reduced ratio. Multiply by 10 or 100 first (1.5 : 2 : 2.5 becomes 15 : 20 : 25, which reduces to 3 : 4 : 5).
• Using the percentages as parts of two terms. Each share is relative to the sum of all three terms, so one term's share changes whenever another changes.
• Entering a zero term and expecting a reduced ratio. A ratio with a zero stays as entered (0.00 : 2.00 : 4.00 rather than 0 : 1 : 2), although the percentages are right.
• Reading 1 : 3 : 4 as 1 part to 3 parts in total. It means the second term is 3 times and the third is 4 times the first.