Vision Display Terminal Calculator

This calculator scores a computer workstation against common visual display terminal (VDT) ergonomic guidance drawn from OSHA's Computer Workstations eTool — which recommends the top of the monitor be positioned at or just below eye level — and the same general screen-height and viewing-distance principles published in the ANSI/HFES 100 human-factors standard for computer workstations. Eye strain risk (0-100) is a composite penalty score, not a measured outcome: it adds 15 points if Screen distance (cm) falls outside the 50-70cm optimal band, another 15 if it's under 45cm (a stacking penalty for a distance close enough to strain accommodation), 10 points if Screen top relative to eyes (cm) sits above eye level rather than at or below it, 10 more if the screen is large (over 30") and close (under 60cm) at the same time, and a scaling penalty of 8 points per hour once Daily screen hours exceeds 6 -- so a 10-hour day alone adds 32 points before any positioning issue is even considered. Viewing angle (degrees) is a straightforward arctangent of Screen top relative to eyes over Screen distance, reporting the true geometric angle rather than a rule-of-thumb estimate. Optimal distance (cm) scales with Screen diagonal (inches) using a rough 1.2x-diagonal rule of thumb (converted to cm), a commonly-cited desktop- monitor heuristic rather than a fixed regulatory figure.

Min font size (pt) derives from the minimum character height that subtends a comfortable angle at the given Screen distance, converted from millimeters to points. 20-20-20 breaks/day is simply three per hour of Daily screen hours, following the popular 20-20-20 rule (every 20 minutes, look at something 20 feet away for 20 seconds). Adjustments needed tallies how many of these checks came back unfavorable. Treat every output as general workplace-ergonomics guidance, not an occupational health diagnosis or a substitute for an individual vision/ergonomic assessment.