How to use this calculator
Enter a total and the two ratio weights. Add A+B to find the total number of parts, then allocate total×A/(A+B) to the first share and total×B/(A+B) to the second. Weights do not need to add to 100.
Formula
A + B = S; first = total × A ÷ S; second = total × B ÷ S
Worked example
Dividing 120 in the ratio 2:3 gives five parts. Each part is 24, so the first share is 48 and the second is 72. Their percentages are 40% and 60%, and they add back to 120.
Assumptions and limitations
Nonnegative totals and weights only, with at least one positive weight. Fractional shares are not rounded into whole items or cents automatically. If dividing indivisible objects or money, choose and disclose a rounding rule; displayed rounded shares may not add back exactly.
Frequently asked questions
Can the total be zero or one weight be zero?
Yes. A zero total gives two zero shares. A zero weight receives nothing, while the other weight receives the entire total. Both weights cannot be zero.
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.