Ratio Calculator
Free to use, with no sign up. Your entries stay in this browser; calculations run on your device.
Result
Simplify: convert decimal terms to integers, divide both by their greatest common divisor. Solve: ? = B × C / A. Scale: k = target / A, target / B or target / (A + B); new ratio = (A × k):(B × k).
Common Core mathematics standard 6.RP.A.3 describes equivalent ratios. The formulas above follow by applying the same scale factor to both terms.
Worked example: 12:18 simplifies to 2:3. 2:3 = 8:12. Scaling 2:3 to a total of 100 units gives 40:60 units. 1.5:2.5 simplifies to 3:5.
Terms must be nonnegative, with at least one nonzero. To solve C:?, A must be greater than zero. A scale target can set A, B, or their combined total. Use the same units before comparing terms; scaled amounts keep those units. Decimal simplification uses the entered number representation exactly; solved and scaled values use decimal arithmetic.
How to use this tool
Choose simplify, solve a missing term, or scale to a target. Enter nonnegative A and B in comparable units; complete C or the target when needed, then Calculate.
Frequently asked questions
Can I simplify decimal ratios?
Yes. The calculator converts the numeric decimal representations to integers using a common power of ten, then divides by their greatest common divisor. For example, 1.5:2.5 becomes 3:5.
Can either term be zero?
One term may be zero, but both cannot be zero. Solving A:B = C:? requires A greater than zero. Scaling a zero term to a target is undefined and is rejected.
How does scaling to a total work?
The target is divided in proportion to A and B: the new A is target × A / (A + B), and the new B is target × B / (A + B). For 2:3 and a total of 100, the result is 40:60.