Screen Size Calculator
Calculate screen dimensions from diagonal and aspect ratio — get width, height, area in square inches, PPI, and megapixels for any display. Free online screen size calculator for monitors, TVs, phones, and projectors.
About This Calculator
The Screen Size Calculator helps you determine the physical dimensions of any display — monitor, TV, laptop, phone, tablet, or projector — from its diagonal measurement and aspect ratio. Simply enter the diagonal size in inches, choose a common aspect ratio like 16:9, 16:10, or 21:9 (or enter a custom ratio), and optionally provide the screen resolution to get PPI and pixel density metrics.
The calculator uses the Pythagorean theorem to derive width and height from the diagonal and aspect ratio: height = diagonal / √(aspectRatio² + 1), width = aspectRatio × height, and area = width × height. When resolution is provided, PPI (pixels per inch) is computed as the diagonal pixel count divided by the physical diagonal. This is the same methodology used by TV manufacturers and display reviewers worldwide.
Regional Notes
India (IN): Screen sizes are typically listed in inches. Common TV sizes range from 32" to 75". A 43" 16:9 TV has a width of approximately 37.5" (95 cm) and height of 21.1" (54 cm). For GST and import duty purposes, displays over 32" may have different tax classifications.
United States (US): Screen size is universally listed in inches. The FTC requires that TV and monitor diagonal measurements be based on the actual viewable area. Common monitor sizes are 24", 27", and 32". Cinema projectors use screen width as the primary spec, with a standard 16:9 or scope (2.39:1) aspect ratio.
United Kingdom (UK): Display sizes are sold in inches. The average UK household uses a 40-55" TV. The UK also commonly uses centimetres for installation and mounting measurements — multiply inches by 2.54 to convert. For example, a 55" TV has a 139.7 cm diagonal.
Frequently Asked Questions
How do I calculate screen size from diagonal and aspect ratio?
Use the formula: height = diagonal / √(aspectRatio² + 1) and width = aspectRatio × height. Then multiply width by height to get the screen area in square inches. Our calculator does this instantly for any diagonal and aspect ratio combination.
What is the difference between screen size and aspect ratio?
Screen size refers to the diagonal measurement of a display, typically in inches. Aspect ratio is the proportional relationship between width and height (e.g. 16:9). A 27-inch monitor and a 55-inch TV can both have a 16:9 aspect ratio, but their physical dimensions differ.
How is PPI calculated for a screen?
PPI (pixels per inch) is calculated by dividing the diagonal resolution in pixels by the diagonal screen size in inches. Diagonal resolution = √(horizontalPixels² + verticalPixels²). For a 27-inch 4K screen (3840x2160): PPI = √(3840² + 2160²) / 27 ≈ 163 PPI.
What are the common aspect ratios for monitors and TVs?
16:9 is the most common aspect ratio for HDTVs, monitors, and laptops. 16:10 is popular on computer monitors for extra vertical space. 4:3 was standard for older TVs and projectors. 21:9 and 32:9 are ultrawide formats used in gaming and professional monitors.
Does a larger diagonal always mean a bigger screen area?
Not necessarily. A narrower aspect ratio (taller) at the same diagonal produces less area than a wider one. For example, a 6.1-inch phone with a 19.5:9 ratio has roughly the same area as a 5.5-inch phone with a 16:9 ratio due to the difference in aspect ratio.
What is a good PPI for a monitor?
For desktop monitors, 90-110 PPI is standard and comfortable at typical viewing distances. Above 140 PPI (retina-class) the human eye can no longer distinguish individual pixels at normal viewing distance. Common examples: 24-inch 1080p = 92 PPI, 27-inch 1440p = 109 PPI, 27-inch 4K = 163 PPI.
How do I measure screen size in inches and centimeters?
Screen diagonal is measured from one corner to the opposite corner of the actual display area (not including bezel). 1 inch = 2.54 centimeters. Our calculator accepts diagonal in inches and computes all dimensions; to convert cm to inches, divide by 2.54.