The formula for calculating total water potential is matric or capillary potential + solute or osmotic potential + pressure potential or turgor pressure + gravitational potential. Water potential is a physical property that predicts the direction of water's flow, based on conditions such as pressure and solute concentration. It is typically represented in formulas by the Greek letter "psi."
The different potentials used in the formula for water potential are generally defined as the differences between positions, instead of absolute values. For example, gravitational potential is measured in the difference in height from the ground. In plants, the height is small and therefore often left out of the equation, except in the case of tall trees.