Proportion Solver
Solve a/b = c/d style proportions instantly by choosing which value to solve for.
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12
Solving for D
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Pick which of the four values (A, B, C, or D) you want to solve for, fill in the other three, and the proportion a/b = c/d is solved instantly using cross-multiplication. Runs fully in your browser.
How to use
- Choose which value (A, B, C, or D) you want to solve for.
- Enter the other three known values.
- Read the solved value computed via cross-multiplication.
Frequently asked questions
- What formula does it use?
- It cross-multiplies the proportion a/b = c/d, e.g. solving for d gives d = (b × c) / a.
- What if a required denominator is zero?
- Division by zero makes the proportion unsolvable, and the tool shows an invalid result in that case.
- Can I use decimals?
- Yes, all four values accept decimal numbers, not just whole numbers.