I've heard an ounce of green to a pound of butter. A stick of butter is 4 oz. 4*4=16.
So then it's a quarter (7g) of weed per stick. A stick of butter is also 1/2 cup. Most Brownie mix boxes ask for 1/2 cup of OIL per batch. I am not sure if you can just substitute butter, someone else would have to say. One batch of brownies makes "thick" brownies at 13x9, "thicker" brownies at 9x9, and "thickest" brownies at 8x8. Figure you do the 13x9, that's 117 sq. in. of brownies, divide that by 7 (for the 7g) and you get 16.714286. So thats roughly a 4x4 brownie for one gram of marijuana.