TV Viewing Distance Calculator
How far to sit from a TV or monitor of a given size: the 30° and 40° field-of-view guidelines (SMPTE and THX), and the distance at which single pixels stop being visible at its resolution.
Result…
How it's calculated
Width = diagonal × a ÷ √(a² + b²), height = diagonal × b ÷ √(a² + b²) for an a:b screen Distance for a field of view θ = width ÷ (2 × tan(θ ÷ 2)): θ = 30° (SMPTE), 40° (THX) Pixel pitch = width ÷ pixels across · pixels vanish beyond pitch ÷ (2 × tan(0.5 arcminute)) Pixel density (PPI) = pixels across ÷ width in inches
Finds the screen's width and height from its diagonal and shape, then the distance at which it fills a given angle of your view. A 30° field of view is widely quoted as the SMPTE guideline for general viewing, and about 40° is quoted as the THX recommendation for a cinema-like seat; the THX viewing guide gives it as a screen diagonal of 0.835 times the seating distance, which is 40° on a 16:9 screen. The pixel figure uses 1 arcminute, the detail a person with normal (20/20) vision can just make out: beyond that distance neighbouring pixels blur together, so extra resolution brings less. Sizes convert exactly, 1 inch = 2.54 cm and 1 foot = 12 inches. This is geometry, so it fits monitors and projector screens too.
Your numbers, step by step
About the TV Viewing Distance calculator
This viewing distance calculator tells you how far to sit from a TV, monitor or projector screen. Enter the diagonal in inches or centimetres and the resolution, and it works out the screen's width and height, then three distances. The first is where the screen fills 30° of your view, widely quoted as the SMPTE guideline for everyday viewing. The second is the 40° view quoted as the THX recommendation for a cinema-like seat, which matches the THX viewing guide rule of a diagonal 0.835 times the seating distance. The third is the distance beyond which single pixels are too small to see with normal (20/20) vision, using the 1 arcminute acuity limit. Distances show in metres or feet, and you can enter your own seating distance to see the angle the screen fills there. The steps show the geometry with your numbers.
How to use it
- Choose inches or centimetres in “Screen size in” and enter the “Screen diagonal”.
- Pick the “Resolution”, or “Other” to type the pixels across and down.
- Leave “Aspect ratio” as “Same as the resolution” unless the screen is sold with a different shape.
- Choose metres or feet in “Show distances in”, and add “Your viewing distance” if you want the angle at your seat.
- Read the 30° and 40° distances and the distance at which pixels stop being visible.
Worked example
A 65 inch 4K (3840 × 2160) TV is 65 × 16 ÷ √(16² + 9²) = 56.7 in (143.9 cm) wide and 31.9 in (80.9 cm) tall. A 30° view needs 56.7 ÷ (2 × tan 15°) = 8.81 ft (2.69 m), and a 40° view 56.7 ÷ (2 × tan 20°) = 6.49 ft (1.98 m). With 67.8 pixels per inch, single pixels stop being visible beyond 4.23 ft (1.29 m). From a sofa 9 ft away the screen fills 29.4° of your view.
Updated
Questions people ask
How far should I sit from a 55 inch TV?
For a 16:9 screen, the 30° guideline puts you about 1.63 times the diagonal away and the 40° guideline about 1.2 times, so roughly 7.5 ft (2.27 m) and 5.5 ft (1.67 m) for 55 inches. Pick within that range by taste: closer is more immersive.
What is the formula for TV viewing distance?
Distance = screen width ÷ (2 × tan(angle ÷ 2)), where the width comes from the diagonal and aspect ratio. For 30° that is width ÷ 0.5359, for 40° width ÷ 0.7279.
At what distance does 4K stop making a difference?
Once a single pixel subtends less than 1 arcminute, a person with normal vision can't pick it out, so farther than the pixel distance shown, extra resolution adds less. On a 65 inch 4K screen that point is about 4.2 ft (1.3 m); 1080p on the same screen reaches it at about 8.5 ft (2.6 m).
Is the SMPTE 30 degree rule a strict standard?
It is a widely quoted guideline for a comfortable field of view, not a rule. Many people sit nearer for films and games, and farther for news and casual viewing.
What mistake do people make when measuring viewing distance?
Measuring from the wall or the back of the sofa instead of from your eyes to the screen. Also, the diagonal is the picture area, not the frame. For pixel density alone, try the pixels per inch calculator.
Does this account for my eyesight and the content?
No. It assumes 1 arcminute of acuity, typical of normal 20/20 vision; sharper or weaker eyes change the pixel distance, and streaming compression or upscaled content can look soft at any distance. For questions about your own vision, ask an optometrist.