Quick, clean, and to the point

Calculate a ratio from two numbers

Excel formula: Calculate a ratio from two numbers
Generic formula 

To generate the ratio of two numbers to each other (e.g. 4:3, 16:9, etc.), you can do using division, the GCD function, and concatenation. In the generic form of the formula (above) num1 represents the first number (the antecedent) and num2 represents the second number (the consequent).

In the example, the active cell contains this formula:


Note: the GCD function only works with integers.

How this formula works

This formula looks complicated, but, at the core, it is quite simple, and created in two parts like so:

= (formula for number1) &":"& (formula for number2)

On the left, the GCD function is used to calculated the greatest common divisor (GCD) of the two numbers. Then the first number is divided by the GCD. On the right, the same operations are performed with the second number.

Next, the result of the right and left operations are joined together using concatenation, with the colon (":") as a separator. So, altogether, we have:

=B4/(GCD(B4,C4)) &":"& C4/GCD(B4,C4)
=1280/(GCD(1280,720)) &":"& 720/GCD(1280,720)
=1280/80 &":"& 720/80
=16 &":"& 9

Note that the final result of this formula is a text value.

Dave Bruns

Excel Formula Training

Formulas are the key to getting work done in Excel. In this step-by-step training, you'll learn how to use formulas to manipulate text, work with dates and times, lookup values with VLOOKUP and INDEX & MATCH, count and sum with criteria, dynamically rank values, and create dynamic ranges. You'll also learn how to troubleshoot, trace errors, and fix problems. Start building valuable skills with Excel formulas today. Learn more.

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