How to Calculate a Digital Camera's Resolution from its Pixel Count

Last Updated: March 4, 2021

If you only know the pixel count (i.e. the number of megapixels) that a digital camera has, it's simple to calculate the linear resolution from it (i.e. the width and height of the resulting images) if you know the camera's aspect ratio. We're going to be using an imaginary 12-megapixel digital SLR with a 3:2 aspect ratio in our examples.

Steps

1
Find out the aspect ratio of your camera. Here are the two most common:
- 3:2, or 3 horizontal pixels for each 2 vertical pixels, is typical for digital SLRs.
- 4:3, or 4 horizontal pixels for each 3 vertical pixels, is the aspect ratio used by most compact (point-and-shoot) cameras in their still mode.
2
Convert your megapixel count to a total pixel count by multiplying it by 1 million, if necessary.

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3
Get a horizontal-to-vertical and vertical-to-horizontal ratio. You get the horizontal-to-vertical ratio by dividing the first part of your aspect ratio by the second; you get the vertical-to-horizontal ratio by dividing the second part of your aspect ratio by the third. In our 3:2 digital SLR example:
4
Multiply your pixel count by the horizontal-to-vertical ratio, then separately, by your vertical-to-horizontal ratio.
5
Take the square root of your resulting numbers.
6
You now have the resolution of the camera. In the case of our imaginary digital SLR, it was 4243 x 2828.
7
Finished.

Community Q&A

Question

How do I convert a screen's resolution into megapixels?

Community Answer

You need to multiply the width by the height and then divide by 1,000,000. For instance, if you wanted to calculate the megapixels in a 1920x1080 screen, you would multiply 1920 by 1080 to get 2,073,600. When you divide that by 1,000,000, you get 2.07 megapixels.