Ratio Calculator
Ratio Calculator works out Answer and Constant of variation k from Known x, Known y and New x. The default figures on this page give answer of 0.75; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- The ratio is 18 : 24.
- As a decimal: 18 / 24 = 0.75
- Divided by the greatest common divisor of the two whole-number parts: 3 : 4
Its 10 worked examples are re-run on every release, last on 15 September 2026. What changed
What the Ratio Calculator calculates
Finds the constant of variation from a known pair and uses it to predict the other variable for direct, inverse, joint and power (including inverse-square) relationships, solves a proportion a/b = c/x by cross multiplication, and reduces a ratio a : b to its lowest whole-number terms.
How to use this Ratio Calculator
Enter Known x, Known y and New x. Answer updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Answer, Constant of variation k and x in the second situation.
The method follows OpenStax, College Algebra 2e §5.8 "Modeling Using Variation" — direct variation y = kx^n, inverse variation y = k/x^n and joint variation.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I calculate a ratio?
Finds the constant of variation from a known pair and uses it to predict the other variable for direct, inverse, joint and power (including inverse-square) relationships. Open “How this is worked out” beside the result to see each step for your own figures.
How do you calculate a 2 to 3 ratio?
It needs Known x, Known y and New x. Nothing else is required, and the figures stay in your browser.
How to calculate a 2 to 1 ratio?
The result gives Answer, Constant of variation k, x in the second situation, y in the second situation, Equation of variation and What the relationship means, each labelled with its unit so the figure can be read on its own.
What information do I need for the Ratio Calculator?
You need Known x, Known y and New x. The page opens with default figures that give answer of 0.75, so you can see the scale before entering your own.
What does this Ratio Calculator show?
It shows Answer, Constant of variation k, x in the second situation, y in the second situation, Equation of variation, What the relationship means, Ratio a / b as a decimal and Ratio in lowest terms, with the working and any warnings for your entries.
Can I check how the Ratio Calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.