Here's a simple formula for figuring out whether or not you have enough lighting in a room:
First, measure your room's length and width, then multiply to get the square footage.
Next, multiply that number by 1.5 to get the amount of wattage needed to properly light the room.
For example, a 10' by 12' room is 120 square feet...multiplied by 1.5 gives you 180. So in that room, you would want at least 180 watts.
In an area that's meant for specific tasks like a kitchen island or an area for homework, multiply by 2.5 instead of 1.5.
Easy as pie!