How to Calculate the Size of a Digital Image

By Mark Spowart
Digital photos are measured by their pixel dimensions.

Digital pictures are measured not only by their physical size, but also by the size of the file they create when they are saved. There are a number of factors that go into determining the file size. The resolution of the digital camera will affect the file size, as will the compression factor the file was saved in and the DPI (dots per inch).

Right click on the image with your computers mouse and select “Properties” from the drop-down menu.

Write down the pixel dimensions of the image and the bit image the picture was taken with. This information will be visible on this page.

Multiply the length of image by the width of the image by the bit color depth. For example, 1280 x 960 x 16 = 19,660,800 for the total number of bits that are contained in the image.

Convert this number to bytes by dividing by 8. In our example, 19,660,800 / 8 = 2,457,600.

Divide this number again by 1,024 to get the file size in kilobytes (KB). In our example, 2,457,600 / 1,024 = 2,400 KB.

Convert this number into megabytes (MB) by dividing the number by 1024. In our example, 2,400 / 1,024 = 2.34 MB.

About the Author

Since 2002 Mark Spowart has been working as a freelance writer and photographer in London, Canada. He has publication credits for writing and/or photography in Canada, The United States, Europe and Norway, with such titles as "The Globe & Mail," "The National Post," Canada News Wire, Sun Media and "Business Edge" magazine.