There are a few ways to measure the size of your computer monitor, depending on whether you want to know the display area, aspect ratio, or diagonal. All of these measurements are easily determined using a ruler or tape measure and some simple math.
Part 1 of 2: Determining the image area
Step 1. Measure the length of the display
Measure the horizontal length of the display from one end to the other with a ruler. Do not include the frame or case around the screen, but only measure the screen.
Step 2. Measure the height of the display
Measure only the display area and not the bezel or housing around the display. Measure the vertical height from the top of the screen to the bottom with a ruler.
Step 3. Multiply the length by the height
To find the display area, multiply the height of the display by the length of the display. Express the image area in 'horizontal length x vertical height'.
For example: If the length is 40 cm and the height is 25 cm, then the image area is equal to 40 x 25 = 1000 cm
Part 2 of 2: Determining the aspect ratio and measuring the screen diagonal
Step 1. Determine the aspect ratio by comparing the length and height
Computer monitors are usually made with an aspect ratio of 4:3, 5:3, 16:9 or 16:10. To find the aspect ratio, compare the length to the height and simplify the numbers if necessary.
- If the length is 40 cm (16 inches) and the height is 25 (10 inches), then the aspect ratio is 16:10.
- If the length is 50 cm and the height is 30 cm, then the aspect ratio is 50:30, which can be divided by 10 so that you get 5:3 as an aspect ratio.
Step 2. Measure the distance between the opposite corners to find the diagonal
The diagonal is what is usually meant when describing the size of the display. Use a tape measure or ruler to find the distance between, for example, the top left corner of the screen and the bottom right corner of the screen. Do not carry the bezel or casing around the screen.
Step 3. Use the Pythagorean theorem to find the length of the diagonal
If the screen is too large to measure the diagonal or you want to avoid scratches and smudges, you can use the Pythagorean theorem to determine the diagonal. Square the height and width of the screen, add the two results, then calculate the square root of the sum to find the length of the diagonal.
For example, suppose the height is 25 cm, then multiply that by itself (25x25=625). Then multiply the length, 40 cm, by itself (40x40=1600). Add the two numbers together (625+1600=2225) and then calculate the square root of this sum (√2225=47, 17)
- You can also find the monitor size by looking up the monitor model number on the manufacturer's website or through a search engine.
- There are several websites that will determine the size of a computer monitor for you based on the number of pixels they detect, such as