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Cross Multiply Calculator

Cross Multiply Calculator


Enter any 3 known numbers to find the fourth value






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How easy was it to use our calculator? Did you face any problem, tell us!

Make free use of this cross multiply calculator to determine the unknown variable value by using the technique of cross multiply fractions. Now the fraction multiplication is now fast and accurate enough with the assistance of this best cross multiplication calculator.

Want to delve into the technique in order to understand? Stay focused and it’s time to move by!

How Do You Cross Multiply?

In mathematical theory:

“Cross multiplication means:

  • The product of numerator in first fraction with the denominator of the second fraction
  • The product of the denominator of the first fraction with the numerator of the second fraction”

This free cross multiply calculator also works on the same criteria aforementioned to generate accurate answers against any fraction problem. Except these calculations, you can also use our simple fraction calculator to add, subtract, multiply, and divide fractions.

Cross Multiplication Formula:

Now you could easily find the missing value of the variable by either using this cross multiplication calculator or the following formula:

$$ \frac{A}{B} = \frac{C}{D} $$

$$ A*D = B*C $$

How To Cross Multiply Fractions?

Let us resolve a few examples to understand the calculations done in this particular method.

Let’s move on!

Example # 01:

How to cross multiply to find x in the proportion pair given below:

$$ \frac{4}{B} = \frac{7}{9} $$


If you want instant calculations, use this best cross multiply calculator. And if you want to understand manually, give a read further!

Cross multiplying fractions:

$$ \frac{4}{B} = \frac{7}{9} $$

$$ A*D = B*C $$

$$ 4*9 = B*7 $$

$$ B = \frac{4*9}{7} $$

$$ B = 5.142 $$

Example # 02:

How to do cross multiplication for the following set of fractions?

$$ \frac{1}{6} = \frac{C}{2} $$


Here we have:

$$ \frac{1}{6} = \frac{C}{2} $$

$$ A*D = B*C $$

$$ 1*2 = 6*C $$

$$ C = \frac{1*2}{6} $$

$$ C = \frac{1}{3} $$

How Cross Multiply Calculator Works?

This cross multiplication calculator will take a couple of seconds to solve for an unknown entity in a set of proportions. Let’s find how!


  • You are given four fields to enter numbers
  • Now what you need to do is enter any three of these numbers in their respective designated fields and leave the fourth as empty
  • Now it’s time to hit the calculate button, so go for it


The free solve for x calculator fractions does the following calculations:

  • Determines the value of the unknown variable in a fraction combination


Why does cross-multiplication compare fractions?

Whenever we make use of the cross product method, the equivalent fractions are not covered in it. This is the reason this particular method does relate all the ratios in order to generate a specific report against the data being provided.

Who invented cross multiplication?

Joseph Louis Langrage, a famous mathematician, introduced the concept of both dot and cross multiplication of fractions by comparing the tetrahedron properties.

Is cross multiplication is used in unitary method?

Yes of course! Cross multiplication is a part of this specific mathematical operation.

Can you cross multiply and divide fractions?

Yes of course! In this particular method, what we need to consider in mind is:

The numerator of the first fraction is multiplied by the denominator of the second fraction. After you get the number, you need to write it as the numerator of the resulting fractions. And in case you find it tricky enough, let this cross multiplication calculator do that for you in a blink of moments.


Usually complex and larger fractions are not easy to explore and reduce. That is why the method of cross multiplication is being introduced to resolve and find solutions to such complicated mathematical problems. And rest when it comes to most accurate and fast outputs of the fraction combinations, this cross multiply calculator will be there to assist you in this regard.


From the source of Wikipedia: Cross-multiplication, Procedure, Use, Rule of three, Double rule of three, 

From the source of Khan Academy: system of equations, elimination, substitution

From the source of Lumen Learning: Solving Proportions, Applications Using Proportions