It can be computed by dividing the location's geopotential number by the normal gravity at 45 degree latitude and zero height, a constant value (9.806199203 m/s2).
As dynamic height is proportional to the geopotential, it remains constant over a given equigeopotential surface.
[2][3] However, because of variations in Earth's gravity, two surfaces having a constant difference in dynamic height or in geopotential do not have a constant geometric distance; for example, they are closer and further apart at the poles and at the equator, respectively.
[4] When differential leveling is done, the path corresponds closely to following a value of dynamic height horizontally, but not to orthometric height for vertical changes measured on the leveling rod.
US National Geodetic Survey data sheets[5] give both dynamic and orthometric values.