Calculating aspect ratio for LCDs/monitors/projectors etc.

I’m working on a new project to compare computer monitors and especially for setting up ideal multi-monitor displays. The idea is to give you as much information as possible on all the monitors out there (using a database), or if your monitor is not in the DB then accept some basic info (diagonal width and resolution) to calculate all the information you need.

So, a basic question for any monitor is: what is the aspect ratio?

Here’s how to calculate the aspect ratio:

I will use Excel functions since they are pretty common… this will also work in OpenOffice/LibrOffice Calc.

Step 1.

Find the greatest common denominator of the horizontal and vertical resolution

Example 1, your everyday 1080p “big screen” LCD TV with 1920×1080 resolution

Use the Excel function “GCD”: GCD(1920,1080) = 120


Example 2, Dell 3007WFP with 2560×1600 resolution

Use the Excel function “GCD”: GCD(2560,1600) = 320

Step 2.

Take the horizontal resolution and divide by the GCD, then take the vertical resolution and divide by the GCD

Example 1, 1080p LCD TV

Horizontal resolution of 1920 / 120 = 16

Vertical resolution of 1080/120 = 9

Example 2, Dell 3007WFP

2560/320 = 8

1600/320 = 5

You now have the aspect ratio!

Simply combine the two results from step 2 and you have the aspect ratio:

Answer 1: Aspect ratio for 1080p LCD TV = 16:9

Answer 2: Aspect ratio for Dell 3007WFP LCD monitor = 8:5

*Note: the 8:5 aspect ratio is commonly referred to as 16:10 (i.e. 8:5 doubled) in order to keep it comparable to 16:9 displays…


These simple steps illustrate the formula that I am using in my app to calculate aspect ratios. If you too are calculating aspect ratios then I hope this was helpful to you! 🙂

NOTE: if you like this, checkout more posts tagged with #OfficeProject… they are all  (at least loosely) related to my quest for the perfect office setup!


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