Viewing Distance & Character Height Calculator
How big does the text on your HMI need to be? Enter the viewing distance and get the minimum legible and the recommended comfortable character height, based on visual-angle rules of thumb used in industrial HMI design.
Model: character height h = D × θ, where θ is the visual angle (5 arcmin for a 20/20 viewer at threshold; 20 arcmin for comfortable industrial reading). Recommended industrial value ≈ distance (m) × 5.8 mm.
FAQ
How large should HMI text be at a given viewing distance?
A common industrial rule is at least 5.8 mm of character height per metre of viewing distance, which corresponds to a 20 arcmin visual angle — about four times the 20/20 threshold. For alarm-critical text, go larger.
What is the minimum readable character height?
The absolute threshold for a person with 20/20 vision is a 5 arcmin visual angle, i.e. about 1.45 mm per metre of viewing distance. This is a laboratory limit, not a design target — always use a comfort margin of 3 to 4 times.
Does this calculator account for lighting and vibration?
No. Poor lighting, vibration, glare and an ageing workforce all reduce effective legibility, so treat the recommended values as a floor for ideal conditions and increase the margin for harsh environments.
Send your timing, brightness or environment requirements — an application engineer replies within 24 hours with matching in-stock models and a quote.
Talk to RONEN →