A Short Course Book
Sensors, Pixels and Image Sizes

Exploring Images Sizes

Click to open an Excel worksheet and use Part 1. Image Sizes to follow the instructions in this section.
Part 1 on the Excel worksheet "Pixels & Images Calculator" calculates the total number of pixels in an image and its aspect ratio when you enter the image's width and height in pixels. The numbers in the descriptions that follow refer to row numbers on the worksheet.

1. Width of image (in pixels) is where you enter the image's width in pixels.

2. Height of image (in pixels) is where you enter the image's height in pixels.

3. Total number of pixels in image is calculated by multiplying the image's width by its height.

4. Aspect ratio is discussed in the next section.


Open the PixelCalc.xls worksheet by clicking the Excel button in this section and enter numbers in the green cells to explore the following questions.

1. Enter the width and height of your own images to find the total number of pixels they contain and their aspect ratio. You can find image sizes in your camera's user guide. There may be more than one resolution, and if so, try them all. When the resolution changes, does the aspect ratio also change?

2. If a digital camera recorded the following image sizes, how many pixels are there in each image size? What is the aspect ratio for each?

. 2,400 x 1,800

. 1280 x 960

. 640 x 480

3. Here are some rectangles commonly found in photography. Calculate the total number of pixels (in the images).

Typical Image Sizes

Computer display

Canon 5D

Canon S3 IS

Width x Height

1024 x 768

4368 x 2912

2816 x 2112

Aspect Ratio

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