How big should a safety sign be? Size and material guide
By Jason Misters. Published 22 October 2026.
A common rule of thumb is that a safety sign can be read from a distance of about the square root of 2000 times its area in square metres. A 150 × 200 mm sign reads at about seven metres and a 300 × 400 mm sign at about fifteen. Choose rigid plastic for durability and vinyl for smooth, clean surfaces.
Choosing size by viewing distance
Sizing guidance in the international signage standards uses a simple relationship between a sign's area and the distance it can be read from. Treat these distances as a starting point and go larger if lighting is poor or people will be moving quickly.
| Sign size | Readable at roughly |
|---|---|
| 150 × 150 mm | about 6 m |
| 150 × 200 mm | about 7 m |
| 200 × 300 mm | about 10 m |
| 300 × 400 mm | about 15 m |
| 450 × 600 mm | about 23 m |
Rigid plastic, vinyl or aluminium
- Rigid plastic (1 mm): the usual choice for walls, doors and posts. It is screwed on or fixed with double-sided pads, and lasts well indoors and in sheltered outdoor spots.
- Self-adhesive vinyl: cheaper and avoids drilling. It suits smooth, clean surfaces such as painted doors, cabinets and glass. Avoid it on textured, dusty or damp surfaces.
- Aluminium: tougher again for harsh outdoor use. Not in our standard range, but we can ask the supplier for a quote.
Signs support workplace controls. They do not replace a suitable and sufficient risk assessment.
Frequently asked questions
What is the most common safety sign size?
For doors and small rooms, 150 × 200 mm. For corridors and yards, 300 × 400 mm. For entrances where the sign is read from a distance, 450 × 600 mm.
Can I use vinyl signs outside?
Vinyl can work on smooth, clean outdoor surfaces, but it is more likely to peel in weather and when knocked. Rigid plastic is the safer choice outdoors.
Signs mentioned in this guide
Sources and further reading
This guide is general information for workplaces in Great Britain, not legal advice. Signs support workplace controls; they do not replace a suitable and sufficient risk assessment.