There are several ways to measure a computer monitor, depending on whether you want to know the image area size, aspect ratio, or diagonal. All of these measurements are easy to get with a ruler or tape measure and simple math.
Part 1 of 2: Defining the area of an image
Step 1. Measure the length of the monitor screen
Use a ruler to measure the horizontal length of the monitor, from end to end. Do not include the frame or the area around the monitor, measure only the screen.
Step 2. Measure the height of the monitor screen
Measure only the image area, not the bezel or border around the monitor. Use the ruler to determine the vertical height, from top to bottom.
Step 3. Multiply the length by the height
To determine the image area, multiply the monitor height by its length. Express the area of the image using the horizontal length x vertical height formula.
For example, if the length is 16 inches (40.5 cm) and the height is 10 inches (25.4 cm), then the image area can be found by multiplying 16 by 10, which is 160 inches (406.4 cm)
Part 2 of 2: Determining Aspect Ratio and Diagonal Size
Step 1. Determine the aspect ratio by comparing the length and height
Computer monitors typically have an aspect ratio of 4: 3, 5: 3, 16: 9, or 16:10. To figure out the aspect ratio, use a fraction to express the length to height ratio and reduce the fraction if necessary.
- If the length is 16 "(40.6 cm) and the height is 10" (25.4 cm), then the aspect ratio will be 16:10.
- If it is 25 inches (63.5 cm) long and 15 inches (38.1 cm) long, then the aspect ratio is 25:15. The fraction can be reduced by 5 and get a ratio of 5: 3.
Step 2. Measure the distance between opposite corners to find the diagonal
The size of a monitor usually means the size of its diagonal. Use a tape measure or ruler to find the distance, for example, from the top-left corner of the screen to the bottom-right corner of the screen. Do not include bevel or frame around the screen in the measurement.
Step 3. Use the Pythagorean theorem to determine the diagonal distance
If the screen is too big to measure diagonally, or you don't want to get dirty, use the Pythagorean theorem to determine the diagonal distance. Take the values of the squares of the height and width of the screen, add them and then extract the square root from the resulting sum, which will be the value of the diagonal.
For example, if the height is 10 inches (25.4 cm), multiply that by yourself (10x10 = 100). Then multiply the length value, 16 inches (40.6 cm), by itself (16x16 = 256). Add these two numbers together (100 + 256 = 356), then find the square root of the sum (√356 = 18.9)
- The monitor size can also be found from the monitor model number on the manufacturer's website or through a search site.
- There are several sites that will determine the size of a computer monitor for you based on the number of pixels detected on the screen, for example: