The most important decision when choosing a jumbo clock is digit height: too small and people can’t read it; too large and you pay for size you don’t need.
Practical guide
| Digit height | Comfortable reading distance | Typical locations |
|---|---|---|
| 4″ (100 mm) | up to ~25 m | Offices, labs, classrooms, OTs |
| 6″ (150 mm) | up to ~40 m | Halls, shop floors, waiting areas |
| 8″ (200 mm) | up to ~60 m | Large halls, concourses, warehouses |
| 12″ and larger | 60 m and beyond | Platforms, yards, building facades (to order) |
These are rule-of-thumb figures for comfortable reading. Mounting height, viewing angle, ambient light and LED colour also matter — red and white are generally the most legible in bright areas. If in doubt, choose the next size up, or use Find My Clock.