How to calculate a window size for a new ensuite bathroom

Is there a calculation for window size based on lighting and the area/volume of the room?

I've got a new ensuite in an extension 2.5m wide x 2m with a window going on the 2.5m ouside rear wall. The window will be south facing.

Cheers for any info

There is no preferred window size/room volume as far as I know; in fact you don’t even have to have a window! Building regulations only specify a minimum number of air changes/hr which you can easily meet with an extractor fan. As long as you keep to the minimum distance from any external corner, the brick opening & the lintel itself conforms to the regs. you can do what you like really. Other influences are where you put the bath or any shower etc. the pitch of the bricks & brick courses, how much light you want to let in etc.

As example; I put 2 new windows in a South facing wall a couple of years ago; a bedroom wall is 2.5m wide & has a window 1.1 x 1.2m wide; the bathroom wall is 2m wide & has a window 1.1m x 1.0m wide as there is an over bath shower fitted; both rooms are very light & airy.

There is no specific calculation - there are some preferred sizes for openings based on quite a few factors, but its way OTT.

Generally your looking at 1050 deep so that the cill is at a nice height, and width may be governed by the amount of wall left between the proposed opening and any adjacent openings (min 440mm) or corners of the building (min 675mm).

The more light the merrier

[quote="^woody^";p="The more light the merrier[/quote]

Well said that man