are you making a box mix or by scratch? If box mix they are usually either for an 8 x 8 pan or 9 x 13. Either way, the 'usual' edible dose is .35 grams. If you are new to edibles that will be plenty per each brownie. So figure in a 9 x 13 you can get 12 large or 24 small brownies. Multiply .35 by how many brownies and that will tell you how much to use for a batch.