Freyburg (Freyburg, 1972)

UCS = 145 ´ ([10670/Dt] – 31.5)

where:

145 is the conversion factor from Mpa to psi.

10670 is in μs/ft.

31.5 is unitless.

The Freyburg equation is derived from Thuringia sandstones, Germany. No additional information about the core samples is currently available. Applications of this model to sandstones in other parts of the world have resulted in unreasonably high UCS values.