What is the minimum width of a final exit door?

For fire exits, the width is the most important factor, and this is determined by the number of people who are likely to be using a particular exit. Current Building Regulations (Fire Safety, Approved Document B, 2010) specify a minimum width of 750mm for a final exit door, to accommodate a maximum of 60 people. As a matter of interest, the minimum standard dimensions for a fire escape window (as opposed to a door) are 660mm by 1180mm.

If it is subject to the building regulations then Approved Document B Vol 2 Building other than dwelling houses then check out page 37. It states for 60 or less persons, 750mm width, normal door height, with some provisos. However in an existing premises risk assessment applies and it depends on the number of persons, the speed of exit required, the agility of those involved and a full assessment of the risk. For instance if it is for a couple of service engineers working in a plant room it could be acceptable but for an office full of office workers not acceptable. It is up to the Responsible Person's FRA.