How to use it
- Choose Calculate: Viewing distance for a screen or Screen size for a distance.
- Type the Screen size (inches) for a distance, or the Viewing distance (m) for a screen.
- Choose the Resolution of the screen, or Other, typed below and type the Width (pixels) and Height (pixels).
- Read the Recommended range, and the single figures for THX, SMPTE and the pixel limit.
Three rules and whose they are
THX recommends a best seat where the screen fills a horizontal angle of about 40 degrees. The Wikipedia article on the optimum HDTV viewing distance gives THX's figure as 40.04 degrees and says it was presented at the 2006 CES show. For a 16:9 screen the distance is about 1.2 times the diagonal.
The 30 degree angle is widely quoted as the SMPTE recommendation for HDTV. The same article says there seems to be no direct recommendation from SMPTE on the question, so this calculator calls it the widely quoted 30 degree figure. For a 16:9 screen it is about 1.63 times the diagonal.
The one arc minute rule comes from the eye. The article says normal (6/6) visual acuity can separate details one arc minute apart, so a pixel that subtends less than that cannot be seen. The Wikipedia article on visual acuity gives the same limit: at 6 metres, 6/6 vision separates contours 1.75 mm apart.
The range and the pixel limit
The recommended range runs from the THX distance, the nearer and more immersive seat, to the SMPTE distance, the farther one. Inside it the screen fills between 30 and 40 degrees of view. If the pixel limit is nearer than the THX seat, no pixels can be seen anywhere in the range. If it falls inside the range, pixels can be seen at the nearer seats, and the note says from where. If it is farther than the SMPTE seat, you must sit farther back than the common recommendation to see no pixels.
width = diagonal × 16 ÷ √(16² + 9²) for a 16:9 screen
THX distance = width ÷ (2 tan 20°); SMPTE distance = width ÷ (2 tan 15°)
pixel distance = (width ÷ pixels across) ÷ (2 tan 0.5′)Screen width and picture height
The distances use the width of the picture, which follows from the diagonal and the pixel grid. The Wikipedia article gives the one-arc-minute distance in picture heights: about 4.8 for 720 rows, 3.2 for 1080 rows and 1.6 for 4K rows. A higher resolution therefore lets you sit closer before the pixels show.
Example: a 55-inch Full HD TV
A 55-inch 16:9 Full HD screen (1920 × 1080) is about 1.22 m wide. Its THX seat is 1.67 m away and its SMPTE seat 2.27 m, so the recommended range is 1.67 to 2.27 m.
Its pixels can be seen from closer than 2.18 m, so the nearest seat of the range shows its pixels slightly. The page says so in a note.
The same grid works the other way round: from 2.5 m, a 4K screen suits 60.5 to 82.2 inches.
| Measure | Value |
|---|---|
| Recommended range | 1.67 to 2.27 m |
| THX 40°, the best seat | 1.67 m |
| SMPTE 30° | 2.27 m |
| No visible pixels from | 2.18 m |
| 4K from 2.5 m, screen size | 60.5 to 82.2 in |
Frequently asked questions
What is the best distance to sit from a TV?
THX recommends the seat where the screen fills about 40 degrees, and the 30 degree figure is widely quoted as SMPTE's. The Wikipedia article notes that no direct SMPTE recommendation was found, so the range is a set of quoted rules rather than one standard.
Why does the range start at THX and end at SMPTE?
The THX seat is the nearer and more immersive one, and the 30 degree seat is farther back. Sitting between them keeps the screen between 30 and 40 degrees of your view.
Does a higher resolution let me sit closer?
Yes. The pixel limit is the distance where one pixel subtends one arc minute. The Wikipedia article gives it as about 3.2 picture heights for 1080 rows and 1.6 for 4K, so a 4K screen can be watched from closer than a 1080p one before its pixels show.
What is an arc minute?
It is one sixtieth of a degree, the angle that normal 6/6 vision can just separate. The Wikipedia article on optimum HDTV viewing distance describes it as the limit of the eye's ability to tell two pixels apart.
Why is the width used and not the height?
The 30 and 40 degree rules are horizontal angles, so they use the width of the picture. The width comes from the diagonal and the shape of the pixel grid, so the calculator follows any grid you type.
Is anything I type sent to a server?
No. The figures are worked out in your browser, and nothing you type is stored or sent to us.
Sources
- Wikipedia: Optimum HDTV viewing distance
- Wikipedia: Visual acuity
- Wikipedia: List of common display resolutions
Figures and text last checked on Tuesday, November 10, 2026.