How this calculator works
The eye should look at or slightly down on the screen centre, so the mounting height follows from the seat and the viewing distance. A common rule is that the sight line to the screen centre should not rise more than about 15 degrees above horizontal. Raising the centre by the viewing distance times the tangent of that angle gives the highest comfortable position. The screen then hangs half its height above and below that centre. The THX and SMPTE distances come from the horizontal viewing angle: a 40 degree angle is THX's immersive recommendation and 30 degrees is the SMPTE minimum, and the distance for either is half the screen width divided by the tangent of half the angle.
Formula
screen width = diagonal x w / sqrt(w^2 + h^2) for a w:h screen, with height = diagonal / sqrt(w^2 + h^2). screen centre height = eye height + viewing distance x tan(maximum downward angle). bottom edge = centre - height / 2, top edge = centre + height / 2. THX distance = width / (2 x tan 20 degrees). SMPTE distance = width / (2 x tan 15 degrees).
Worked example
A 55 inch 16:9 television is 47.94 inches wide or 1.218 metres, and 26.96 inches high or 0.685 metres. With the eye at 1 metre, a viewing distance of 2.5 metres and a 15 degree limit, the highest sensible centre is 1 + 2.5 x tan 15 degrees = 1.670 metres. The bottom edge is then 1.327 metres and the top edge 2.012 metres. The THX distance for this screen is 1.673 metres and the SMPTE distance is 2.272 metres.
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Frequently asked questions
How high should a TV be mounted?
The centre of the screen should sit at or a little above seated eye height, with the sight line no more than about 15 degrees above horizontal. For most living rooms that puts a 55 inch screen centre between about 1.0 and 1.2 metres above the floor.
Does a fireplace above the mantel work?
Usually not for comfortable viewing. A fireplace raises the screen far above eye level and forces the viewer to look up, which strains the neck over a long film. A mantel mount that pulls the television down when in use is one compromise.
How far should I sit from the television?
THX suggests about 1.2 times the diagonal for an immersive 40 degree view, and SMPTE suggests about 1.6 times the diagonal as a minimum comfortable angle. The THX and SMPTE distances on this page give the values for the screen you entered.
Does screen tilt change the answer?
A downward tilt can reduce the apparent angle for a high mount, but it also distorts the picture and catches reflections. Treat tilt as a last resort and lower the mount instead.