What is cross multiplication?

For a/b = c/d, multiplying diagonally gives a times d equals b times c. The missing value can then be isolated with one division.

Can I use decimal values?

Yes. Every known position accepts decimal values where the proportion remains mathematically defined.

Category: Calculators

Solve any missing value in the proportion a/b = c/d.

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Unknown value

Result

d = 6

The value follows from equal cross products: a × d = b × c.

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Details

Choose the missing position and enter the other three values. The calculator solves the proportion and shows the cross-multiplication formula.

It is useful for scaling recipes, drawings, mixtures and any quantities that keep the same ratio.

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Good to know

What is cross multiplication?: For a/b = c/d, multiplying diagonally gives a times d equals b times c. The missing value can then be isolated with one division.
Can I use decimal values?: Yes. Every known position accepts decimal values where the proportion remains mathematically defined.