I am trying to program a MWD (monitoring while drilling) software for a Exploration Driller and I was wondering if the forum could confirm what I have found out. I need to calculate the WOB (weight on bit) and Head Torque, I do the following direct reading: WOB: Pushdown pressure (PSI). = Ppd HoldBack pressure (PSI). = Phb String weight is easily calculated as the sum of the number of rods+head weight+hammer weight. Sw Theoretically the depth of the hole does not matter, air is used to take out the cutting from the bottom hole, so I neglect any buoyancy factor. The WOB result should be WOB=Sw+Fpd-Fhb. Where Fpd is the pushdown thrust calculated as: Fpd=Ppd*(2*pi*Rp1^2) Rp1 is the radious of piston1 Fhb=Phb*(2*pi*Rp2^2) Rp2 is the radious of piston2 For the Torque on the Hammer, I will be equal to the torque generated by the hydraulic motor which rotates it: Direct reading: Pressure of the hydraulic motor (PSI) = Pm Flow Rate of motor=Fm RPM Torque= (Fm*Pm*36.77)/RPM I am confident in the calculation of the torque, not 100% sure about the WOB. Did I semplify the model too much? Are there any other contributes to be taken into account? Thanks to everyone who can help me out with this model.