Bias Light Calculator — LED Strip Behind TV / Screen

Free calculator that sizes an LED bias-light strip for the back of your TV or projector screen. Inputs: diagonal + aspect ratio. Outputs: screen perimeter, LED strip length needed (with slack for corners), target perceived brightness (10% of calibrated screen white per Lloyd Auerbach's SMPTE recommendation) and the colour temperature you must use (D65, 6500K). Bias light reduces eye fatigue in dark viewing rooms and visually boosts contrast by ~15%.

How to install

1
Buy 6500K LED strip

MediaLight, MediaLight Eclipse, Govee Wall-T, or any 6500K (D65) RGB-IC strip — never warm-white.

2
Mount on back of screen

Adhesive strip on the rear edge, 5-10 cm from the wall. Point LEDs toward the wall, not toward the viewer.

3
Set brightness to ~10%

Just enough to softly illuminate the wall around the screen — not so bright that the wall draws your eye.

4
Verify D65

Look at white text on the screen with the bias light on. Should still appear neutral white. If it shifts warm/cool, the strip isn't actually 6500K.

Eye-strain-reducing LED strip dimensioning for TV and projector screens

Screen perimeter
— cm
Sum of all four sides
LED strip needed
— m
Includes ~30 cm slack for corners and margin
Target perceived brightness
— cd/m²
≈10% of calibrated screen white (≈100 cd/m²)
Recommended colour temp
6500 K
D65 (the same as the calibrated screen white)
Bias light reduces eye strain in dark rooms and improves perceived contrast by ~15%. Mount the strip on the back of your screen, ~5-10 cm from the wall, pointing AT the wall (not toward you). Use a 6500K (D65) strip — anything warmer or cooler tints your perception of the screen colours. MediaLight, MediaLight Eclipse, and Govee Wall-T are reputable options.

Features

Aspect-aware perimeter Perceptual brightness target D65 standard
Who is this tool for?
📽️ Projector Owners

FAQ

Why 6500K specifically?

Your eye uses surrounding light to white-balance perception. If the bias light is warm (3000K), your eye adapts toward warm and the screen looks blue. D65 (6500K) matches the screen's calibrated white, so your perception stays accurate.

Will any LED strip work?

No — most cheap "white" LED strips are 3000-4000K (warm white). You need 6500K explicitly. RGB strips set to "white" are typically not D65 either; aim for products specifically labelled "bias light" or "D65 calibrated".

How much does it actually help?

Subjective, but well-documented: less eye strain in long viewing sessions, perceived contrast boost ~15%, no more "hole punched in the wall" effect on a dark scene. THX, ISF and Imaging Science Foundation all recommend it for serious home cinema.

💡 Want us to improve this tool just for you?

We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

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