Reference tools only. Your rig's approved kill sheet, company procedures and the well program govern. Oilfield units.
Hydrostatic pressure
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Formula: HP = MW * 0.052 * TVD
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #13; IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #1
Mud weight to gradient
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Formula: G = MW * 0.052
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #14; IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #2
Pressure to equivalent mud weight
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Formula: EMW = P / (0.052 * TVD)
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #17; IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #3
MAASP
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Formula: MAASP = (MAMW - MW) * 0.052 * shoeTVD
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #25; IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #11; SLP Alaska Well Control Manual (Brian Walden), SLP Alaska Well Control Total.pptx, slide 945
ECD
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Formula: ECD = APL / (0.052 * TVD) + MW
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #18; IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #6
Pipe capacity
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Formula: cap = ID^2 / 1029.4
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #10
Annular capacity
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Formula: cap = (D^2 - d^2) / 1029.4
Source: IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) #11
Open-end steel displacement
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Formula: disp = (OD^2 - ID^2) / 1029.4
Source: IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #17 (metal displacement term); Cudd Well Control Technical Data Book (2021), Formulas & Equations
Closed-end displacement
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Formula: disp = OD^2 / 1029.4
Source: IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #18 (closed end displacement term)
Triplex pump output
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Formula: out = 0.000243 * liner^2 * stroke * eff
Source: Cudd Well Control Technical Data Book (2021), Formulas & Equations
Strokes to bit or bottoms up
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Formula: stk = V / out; time_min = stk / SPM
Source: Cudd Well Control Technical Data Book (2021), Formulas & Equations; IADC WellSharp Drilling Formula Sheet, Field Units, Revision 4 (26 March 2025) kill sheet
Trip sheet: expected fill pulling dry
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Formula: Fill (bbl) = (OD^2 - ID^2) / 1029.4 x length pulled
Source: IWCF Drilling Well Control Formula Sheet (Surface and Subsea, Levels 2 to 4); API RP 59, Recommended Practice for Well Control Operations
Slug weight
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Formula: MWs = MW + Ldry * pipeCap * MW / Vs
Source: Cudd Well Control Technical Data Book (2021), Formulas & Equations; Algebraic rearrangement of IWCF Drilling English API Formula Sheet EX-0035, Version 3.0 (May 2024) #24
Buoyancy factor
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Formula: BF = (65.4 - MW) / 65.4
Source: IADC WellSharp Completion/Workover Formula Sheet, Field Units, Revision 4 (26 March 2025) #3; Cudd Well Control Technical Data Book (2021), Formulas & Equations
Buoyed hook load
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Formula: Hook load (lb) = air weight (lb/ft) x length x BF + block weight
Source: IADC Drilling Manual, 12th ed., hydraulics, kick tolerance and pipe chapters
Free point from stretch
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Formula: L_kft = 1.9635 * S * (OD^2 - ID^2) / PI_klb
Source: Cudd Well Control Technical Data Book (2021), Formulas & Equations
Cement sacks
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Formula: sx = 5.615 * cap * L * excess / yield
Source: Cudd Well Control Technical Data Book (2021), Formulas & Equations
Unit conversions
- 1 ft = 0.3048 m
- 1 in = 25.4 mm
- 1 bbl = 42 gal = 0.158987 m3 = 5.615 ft3
- 1 psi = 6.8948 kPa
- SG = ppg / 8.33
- 1 lb = 0.45359237 kg
- 1 ft-lb = 1.3558 N-m
Source: NIST SP 811 (exact factors); ppg to SG uses 8.33 ppg fresh water per IWCF formula sheet
Make-up torque reference
Values in the original wording of the source. The manufacturer data sheet for the connection in hand governs.
Use manufacturer or API RP 7G values; company chart goes here