TV Size Calculator

The TV size vs. viewing distance calculation tells you the optimal screen size for your room — or the optimal seating distance for a TV you already own. Sitting too close causes eye strain; too far loses picture detail.

Formulas: Recommended Viewing Distance = TV Size × Distance Factor Ideal TV Size = Viewing Distance ÷ Distance Factor TV Height × Width from diagonal:

• Width = Diagonal × cos(arctan(9/16)) ≈ Diagonal × 0.872 (for 16:9)
• Height = Diagonal × sin(arctan(9/16)) ≈ Diagonal × 0.490 (for 16:9)

Distance factor by resolution:

• 1080p (Full HD) — 1.5× to 2.5× the screen diagonal
• 4K (Ultra HD) — 1.0× to 1.5× the screen diagonal (can sit closer without seeing pixels)
• 8K — theoretically 0.75× the screen diagonal (marginal benefit in most rooms)

What each variable means:

• TV Diagonal — how TVs are measured: corner to corner, not width. A “65-inch TV” has a 65-inch diagonal.
• Distance Factor — the multiplier applied to diagonal size to get the ideal viewing range. Lower factor = can sit closer.
• Viewing Angle — SMPTE recommends 30° horizontal viewing angle; THX recommends 36°. Wider angles feel more immersive but may require head movement for the sides.

Quick reference table:

Worked example: Sofa is 9 feet (108 inches) from the TV wall. You plan to buy a 4K TV. Ideal size = 108 inches ÷ 1.25 (midpoint 4K factor) = 86 inches diagonal — so an 85-inch TV is ideal. Choosing a 65-inch 4K TV at 9 feet: 65 × 1.25 = 81 inches (6.8 ft) — you are sitting slightly farther than ideal, losing some immersiveness but still comfortable.

Height consideration: Mount the TV so the center of the screen is at eye level when seated — typically 42–48 inches from the floor to screen center.