Screen Size Calculator

Screen size is measured diagonally from one corner of the screen to the opposite corner. This is the industry standard measurement that is used when advertising display sizes for TVs, monitors, smartphones, tablets, and other devices.

For example, when you see a "55-inch TV," this means the diagonal measurement from the bottom-left to top-right (or top-left to bottom-right) corners is 55 inches. The actual width and height will be smaller than this diagonal measurement.

The relationship between screen size (diagonal), aspect ratio, and dimensions (width and height) is based on the Pythagorean theorem:

• Diagonal² = Width² + Height²
• Aspect Ratio = Width ÷ Height

When you know the diagonal size and aspect ratio, you can calculate the exact width and height. For example, a 55-inch TV with a 16:9 aspect ratio has:

• Width: approximately 48 inches
• Height: approximately 27 inches

Use our calculator above to quickly determine these dimensions for any screen size and aspect ratio.

PPI (Pixels Per Inch) is a measurement of pixel density or resolution that indicates how many pixels are displayed per inch of screen space. It's calculated by dividing the diagonal resolution (in pixels) by the diagonal screen size (in inches).

PPI matters because it directly affects image sharpness and detail. Higher PPI means more pixels in the same physical space, resulting in sharper images and text. The optimal PPI depends on viewing distance:

• 300+ PPI: Ideal for smartphones and tablets (viewed up close)
• 150-250 PPI: Good for computer monitors (viewed at arm's length)
• 40-100 PPI: Sufficient for TVs (viewed from across the room)

Beyond certain thresholds, the human eye cannot discern additional detail, which is why Apple coined the term "Retina display" for screens with sufficiently high PPI that individual pixels are indistinguishable at normal viewing distances.

The most common aspect ratios for modern displays include:

• 16:9 (1.78:1): Standard widescreen format used in most TVs, monitors, laptops, and smartphones
• 21:9 (2.33:1): Ultrawide format popular in cinematic monitors and premium ultrawide displays
• 4:3 (1.33:1): Traditional "square" format used in older TVs and some tablets
• 3:2 (1.5:1): Used in Microsoft Surface devices, some laptops, and DSLR camera sensors
• 32:9 (3.56:1): Super ultrawide format found in specialty gaming and productivity monitors
• 1:1 (1.0:1): Square format sometimes used in specialized applications
• 2.35:1 or 2.40:1: Cinema scope formats used in movie theaters (letterboxed on home displays)

16:9 is by far the most common aspect ratio today, having largely replaced the older 4:3 standard. However, wider ratios are gaining popularity for gaming, productivity, and cinematic experiences.

To calculate the optimal TV size for your room, consider viewing distance as the primary factor:

1. Measure the distance from your seating position to where the TV will be placed (in inches).
2. For a comfortable viewing experience with standard resolution content (1080p):
   • Divide this distance by 2.5 to get the recommended diagonal screen size
   • Example: 10 feet (120 inches) ÷ 2.5 = 48-inch TV
3. For 4K UHD content:
   • Divide this distance by 1.5 for a more immersive experience
   • Example: 10 feet (120 inches) ÷ 1.5 = 80-inch TV

General guidelines:

• Minimum distance: 1.5 times the screen diagonal for comfortable viewing
• Maximum distance: 3 times the screen diagonal to appreciate the resolution
• Field of view: The screen should occupy 30-40 degrees of your field of view for an immersive experience

Also consider room size, wall space, and furniture layout when determining the optimal TV size.

Screen resolution and screen size are independent specifications, but they work together to determine image quality:

• Screen resolution refers to the number of pixels (e.g., 1920×1080 for Full HD)
• Screen size refers to the physical dimensions of the display

When the same resolution is displayed on different screen sizes, the pixel density (PPI) changes:

• Smaller screens with high resolutions have higher PPI, resulting in sharper images
• Larger screens need higher resolutions to maintain the same image quality

Recommended resolutions by screen size:

• 24-32 inch monitors: 1080p (Full HD) to 1440p (QHD)
• 27-32 inch professional monitors: 1440p (QHD) to 4K (UHD)
• 40-50 inch TVs: 1080p (Full HD) to 4K (UHD)
• 55+ inch TVs: 4K (UHD) or 8K for very large screens

The greater the viewing distance, the less important extremely high resolution becomes, as the human eye cannot discern individual pixels beyond certain distances.

To calculate the actual width and height of a screen when you know the diagonal size and aspect ratio:

1. Express the aspect ratio as a fraction (e.g., 16:9)
2. Use the Pythagorean theorem with the aspect ratio to find the dimensions

For a 16:9 display:

1. Let h be the height of the screen
2. The width is 16h/9 (based on the aspect ratio)
3. Using the Pythagorean theorem: diagonal² = width² + height²
4. Substitute: diagonal² = (16h/9)² + h²
5. Solve for h: h = diagonal ÷ √[(16/9)² + 1]
6. Once you have h, calculate width = 16h/9

Or more simply, use our Screen Size Calculator above to instantly calculate these dimensions.

Manufacturers measure only the viewable area of the screen, not the entire device including bezels or housing. This diagonal measurement represents the actual display area from corner to corner.

However, there are some important considerations:

• In the past, with CRT displays, the advertised size sometimes included parts of the tube that weren't actually visible, leading to regulations requiring "viewable image size" listings.
• With modern flat panel displays, the advertised size is generally accurate to the viewable area.
• When planning for space, remember to account for:
  • The bezel (frame) around the screen
  • The stand or mount depth
  • Additional space for ventilation
  • Any attached soundbars or accessories

For precise planning, look for the "dimensions without stand" or "dimensions with stand" specifications provided by manufacturers, which give the full physical measurements of the device.