A head, also called pressure head or hydrostatic pressure, is a unit of pressure for a fluid, commonly used in water pumping and hydro power to express the height that a pump must lift water, or the distance water falls. Head is the weight of a given height (or depth) of water column at its bottom end, expressed as 'meter head' or 'foot head.' It is independent of the amount of water: the pressure head of a 3-meter high or deep 5-centimeter-diameter pipe is the same as that of the 50-centimeter-diameter pipe of the same height or depth.

 

Total head accounts for friction head losses, etc.