Torque & Drag Calculator
Simplified drillstring weight, hookload, and torque estimation for pickup, slackoff, and rotating conditions.
Drillstring Parameters
Buoyed Weight
--
lbs
Pickup (Hookload)
--
lbs
Slackoff (Hookload)
--
lbs
Rotating (Hookload)
--
lbs
Buoyancy Factor
--
Drag Force (Pickup)
--
lbs
Est. Surface Torque
--
ft-lbs
WOB Transfer Eff.
--
Hookload vs. Depth
How this was calculated
Buoyancy Factor: BF = 1 - (MW / 65.5), where 65.5 ppg is steel density.
Buoyed Weight: Wb = pipe_wt × pipe_len × BF
Pickup Hookload: Wb × (cos θ + μ × sin θ)
Slackoff Hookload: Wb × (cos θ - μ × sin θ)
Rotating Hookload: Wb × cos θ (no axial friction)
Torque: μ × Wb × sin θ × r, where r = OD/2 (ft).
WOB Transfer: (cos θ - μ × sin θ) / cos θ. Below 100% means friction reduces effective WOB at bit.
Assumptions: Uniform inclination (no build/drop). Single string. Simplified soft-string model.
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Book a free strategy call →Understanding Torque and Drag in Drilling
Torque and drag are the frictional forces that resist drillstring movement in a wellbore. Drag is the axial friction force experienced during tripping (pickup and slackoff), while torque is the rotational friction during drilling. Both are functions of the normal contact force between the drillstring and the wellbore wall, which increases with inclination, dogleg severity, and string weight.
This simplified calculator uses a soft-string model with a uniform average inclination. It provides estimates for hookload under three conditions: pickup (pulling out, friction opposes movement upward), slackoff (running in, friction opposes downward movement), and rotating (no axial friction, only gravity component). The difference between pickup and rotating hookload gives the total drag force.
WOB transfer efficiency indicates how much of the surface weight applied translates to actual weight on bit. In high-angle wells with high friction, this efficiency can drop significantly, meaning that even heavy strings may not deliver sufficient WOB to the bit without buckling.
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