Proportion Calculator
Solve ratios and proportions from any 3 known values, with clear steps.
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How to use Proportion Calculator
- 1Enter any 3 values in A/B = C/D.
- 2Leave the value you want to solve blank.
- 3Select Solve Proportion.
- 4Review the answer and cross-multiplication explanation.
How the Proportion Formula Works
For A/B = C/D, cross multiplication gives A × D = B × C. The calculator rearranges that equation for whichever single position you leave blank and shows the substituted values.
Frequently asked questions
What is a proportion?
A proportion states that 2 ratios are equal, such as 2/3 = 4/6.
Which value can be missing?
Any one of A, B, C or D can be blank. The calculator solves that position from the other 3 values.
Can I use decimals?
Yes. Positive and negative decimal values are supported, except a denominator cannot be zero.
Is the calculation private?
Yes. It runs entirely in your browser.