That depends on the amount of light output in lumens (or candela...) from your sconces and where they are situated.

We have two sconces in our powder room and they provide more than enough light. They are on a dimmer and are never turned full-on except when I am cleaning the room.

thanks. i've not purchased the sconces yet so i'm not sure. guess i should just look for some with very bright capability. any wattage suggestions total for each sconce? thanks.

A 60w a19 incandescent would provide ~ 800+ lumens. A 26w cfl ~ 1500+ lumens. Assuming ~ 20 lumens per sq ft, your total is 8*8*20=1280 lumens.

Okay, so where can the rest of us find this magic formula?

Our architect had come up with a lighting scheme, that when my husband saw it (I was out of town), he kept saying "more light! more light!" Now the project manager seems to think we will be almost blinded in a couple of the rooms and the basement. I sort of get lumens - they follow the inverse square law of light, right, so that the closer the light source is, the greater the lumens, no matter what power the light has?

is there some chart that offers suggestions for LUMENS by room size?
Retired English teacher here--math definitely not my strong point--
and need to change out all light fixtures in house we bought in FL as second home
Master bath has only 1 window in the shower so natural light is nonexistant in sink areas
we are going to use ceiling fans w/lights in bedrooms for overhead lights but the rooms are small and if we can use 1 globe vs the 4 light fixture it probably would be nicer look

The crude way of estimating is to use the following formula

Length * Breadth * (desired lumens per sq ft) = total lumens for the room

The formula assumes
1. Ceiling height between 8 - 10 ft.
2. No consideration for shading caused either by the fixture (e.g. - recessed cans, lamp shades).
3. Light sources are diffuse and non directional.
4. Lights are pointing downwards. Indirect lighting (e.g. - cove lighting) requires more since the ceilings are usually higher than normal and the lights are directed upwards.

davidtay, are you suggesting length x breadth + total lumens for the room? this would mean only 64 lumens for our room? i have no idea if that is enough. do you suggest i look for sconces with a downward or upward pointing light? i'd assume upward, but i have no idea. i was thinking to look for 150 total watts for the room. might that be good?

length * breadth * (lumens per sq ft)

For example (living space at 20 lumens per sq ft)
17 * 18 * 20 = 6120

or for a kitchen area (@ 35 lumens per sq ft)
20 * 15 * 35 = 10500

"That depends on the amount of light output in lumens"

Are the sconces controlled by a switch at the door?

Every habitable room is required to have a switched outlet.

In the NEC an "outlet" is a place something is or can be connected to power.

A ceiling fixture (or wall) is an outlet, as is a switched receptacle a lamp can be plugged into.

The amount of light is not really a code issue, but a personal choice.

As long as you are redoing the room I would add an overhead light on a separate control.

we're not redoing the room :(

the sconces will be controlled by a wall switch as you enter the room.

In our last house the powder room had about the same sqare feet as yours does, just different dimensions. We had three halogen lights above the mirror and that was plenty of light for everyday use. I don't remember the actual bulb we used as we haven't lived there for almost a year. Just look for sconces that allow a brighter bulb or that use two bulbs in each sconce. I would use the lumen formula davidtay posted above. That will help you decide if the sconces you like will be bright enough. We did have a bathroom fan with a light installed above the toilet. That helped for when I wanted to clean the bathroom, or needed a brighter light for removing slivers, etc. as the bathroom was where we kept our first aid kit, but we could have gotten along fine without it as the light from the vanity fixture was enough for the room.

Still I would take this opportunity to add an overhead light. If you concentrate the light in sconces you may end up with bright light casting shadows. An overhead will add light reflected back by the mirror and allow the sconces to use lower lumen bulbs. It will give more balance to the lighting.