We were trying to figure out how to determine the area of something yesterday and I found the following websites. I am sure there are others that have formulas for areas, but these pretty much give you all the information you need. I like the second link a little better, but if you simply need to PRINT out the formulas, the first one will work.
Here is website that has the formulas for how to determine area for various shapes – triangles, circle, etc.. This one is very basic.
This one has the same formulas, but goes into a little more description on how to actually USE the formula information. I like that and it’s helpful for students who haven’t done a lot of geometry.