The formula for calculating the proper amount of light you should have in each room of your home:
*Multiply the length times the width of the room (in feet). Then, multiply that number times 1.5. This number gives you the amount of wattage needed to light the room properly for general illumination (based on standard incandescent bulbs).
*For task lighting in areas where stronger light is needed (such as a kitchen island), multiply the area's square footage by 2.5 rather than 1.5 to find the needed wattage.