How many lemons to use to make a gallon of water?

To make a gallon of lemon water, you'll typically need about 8 to 12 lemons, depending on how tart you want the flavor. One lemon generally yields about 2 to 3 tablespoons of juice, so you can adjust the number of lemons based on your taste preference. For a balanced flavor, aim for around 1 to 1.5 cups of lemon juice mixed with the gallon of water.