You may have used carbon footprint calculators or ecological footprint calculators; now there is one for calculating your water footprint, too.
The Calculator gives you an estimate of the total amount of water you use, what is called your water footprint. The Calculator takes into account not only the water used in your home, but also the water used to produce the food you eat and the products you buy. Your water footprint includes other factors such as water utilized to cool power plants that provide your electricity, and water saved when you recycle. You may not drink, feel or see this water, but it makes up the great majority of your water footprint.
This calculator works only in the US though but there are links provided for similar calculators that work with worldwide locations even though they are not as neat to use.