How to use this calculator
Enter A and B in the same units. The calculator clears decimal denominators, finds the greatest common divisor and divides both integerized values by it. Changing only one part changes the relationship.
Formula
A : B → (A × L ÷ GCD) : (B × L ÷ GCD)
Worked example
150:250 reduces to 3:5 because both values divide by 50. The decimal ratio A/B is 0.6. As shares of the combined total, the parts are 3/8 = 37.5% and 5/8 = 62.5%. The decimal input 1.5:2.5 also reduces exactly to 3:5.
Assumptions and limitations
Nonnegative values only. A ratio with one zero part reduces to 0:1 or 1:0; 0:0 has no meaningful reduction. A/B is undefined when B is zero, although a part-to-part relationship 1:0 can still describe all of a quantity in the first part.
Frequently asked questions
Can I simplify a decimal ratio?
Yes. For 0.75:1.25, clearing the decimal denominators gives 3:5. Decimal reduction uses exact fractions, rather than a floating-point greatest-common-divisor approximation.
How precise are the results?
Finite decimal inputs are converted to fractions and reduced with integer arithmetic. Fractions and reduced ratios are exact within the input limits. Decimal displays use up to six places, or scientific notation for tiny nonzero results.
Does 2:3 mean the first part is two thirds of the total?
No. In a part-to-part ratio of 2:3, the total has five parts. The first share is 2/5 (40%) and the second is 3/5 (60%).
Exact reduction; decimal displays may be rounded.