How much light do you need in a room?

I come across homes all the time that have inadequate lighting, lamps and fixtures. It's a bit like getting dressed up and forgetting your jewelry.

Calculate the amount of light needed in any room by multiplying the length times the width of the room (in feet). Then multiply that number by 1.5. This gives you the number of watts required to provide ambient lighting for the room. If task lighting is needed, multiply the square footage by 2.5 instead of 1.5 to find the wattage. Ceiling fixtures should be at least 7 feet above the floor.

Examples:
1) 12’ x 16’ = 192’ square footage
192' x 1.5 = 288watts
Therefore a 12’ x 16’ room would have ample lighting with two 150-watt table or floor lamps
(2 x 150 watts = 300 watts) or an 8-light chandelier with 40-watt bulbs (8x 40 watts = 320
watts).

2) For specific task lighting within a space (for example, the light needed on a kitchen island ), multiply the square footage of the island (8’ x 4’ = 32’) times 2.5. Two 40-watt mini pendants would do the job (32’ x 2.5 = 80 watts).

Other links & sources:
Massive Lighting - an average (in Watts) in order to have good light
Common Kitchen Lighting Mistakes
Lowes Lighting Tips
Energy Saving Lighting Tips