How much chlorine needs per square foot should be added to a swimming pool?

Buy a good test kit and follow instructions. If after you have added chlorine to the pool and you get little or no reading on the test kit then you did not add enough chlorine. Keep doing this until you get the proper readings, usually 1.5 to 3.0, and that is what it takes to bring levels to proper levels this time. Next time it may take more or it may take less depending upon bather load.