Drilling Mud Weight Calculator
Convert drilling fluid weight between ppg, psi/ft, SG, kg/L, kg/m³ and lb/ft³; get hydrostatic pressure (ppg × 0.052 × TVD ft), ECD, kill mud weight (MW + SIDPP ÷ (0.052 × TVD), rounded up) and maximum allowable mud weight from a leak-off test.
Use the Drilling Mud Weight Calculator
Mud Weight Input
Enter a mud weight value to see conversions and calculations.
Mud Weight Conversions
psi/ft uses the oilfield constant 0.052; SG uses fresh water = 8.345 ppg.
Hydrostatic Pressure at TVD
P (psi) = MW (ppg) × 0.052 × TVD (ft); P (kPa) = SG × 9.80665 × TVD (m)
Equivalent Circulating Density (ECD)
ECD (ppg) = MW + Ann. loss (psi) ÷ (0.052 × TVD ft)
Kick: kill mud weight
| Kill mud weight | — |
| Exact value | — |
| Formation pressure | — |
| Mud weight to balance pore pressure | — |
KMW = MW + SIDPP ÷ (0.052 × TVD ft), rounded up to 0.1 ppg. Required MW = (pore pressure + overbalance) ÷ (0.052 × TVD).
Leak-off test: MAMW and MAASP
| Max allowable mud weight | — |
| Fracture gradient at shoe | — |
| MAASP with current mud | — |
MAMW = LOT ÷ (0.052 × shoe TVD) + test MW, rounded down to 0.1 ppg. MAASP = (MAMW − MW) × 0.052 × shoe TVD.
Mud weight conversion table
Hydrostatic pressure at 10,000 ft TVD (3,048 m) uses ppg × 0.052 × depth.
| Fluid | ppg | SG | kg/m³ | lb/ft³ | psi/ft | psi @ 10,000 ft |
|---|---|---|---|---|---|---|
| Fresh water | 8.35 | 1.000 | 1,000 | 62.4 | 0.434 | 4,339 |
| Seawater | 8.55 | 1.025 | 1,025 | 64.0 | 0.445 | 4,446 |
| 9 ppg mud | 9.00 | 1.078 | 1,078 | 67.3 | 0.468 | 4,680 |
| 10 ppg mud | 10.00 | 1.198 | 1,198 | 74.8 | 0.520 | 5,200 |
| 11 ppg mud | 11.00 | 1.318 | 1,318 | 82.3 | 0.572 | 5,720 |
| 12 ppg mud | 12.00 | 1.438 | 1,438 | 89.8 | 0.624 | 6,240 |
| 13 ppg mud | 13.00 | 1.558 | 1,558 | 97.2 | 0.676 | 6,760 |
| 14 ppg mud | 14.00 | 1.678 | 1,678 | 104.7 | 0.728 | 7,280 |
| 16 ppg mud | 16.00 | 1.917 | 1,917 | 119.7 | 0.832 | 8,320 |
| 18 ppg mud | 18.00 | 2.157 | 2,157 | 134.6 | 0.936 | 9,360 |
| Cesium formate brine | 19.20 | 2.301 | 2,301 | 143.6 | 0.998 | 9,984 |
Worked example: kick at 10,000 ft
Drilling with 11.5 ppg mud, the well is shut in with 312 psi SIDPP at 10,000 ft TVD. Hydrostatic = 11.5 × 0.052 × 10,000 = 5,980 psi; formation pressure = 5,980 + 312 = 6,292 psi. Kill mud weight = 11.5 + 312 ÷ (0.052 × 10,000) = 11.5 + 0.6 = 12.1 ppg, which balances 12.1 × 0.052 × 10,000 = 6,292 psi.
A leak-off test of 1,000 psi at a 4,000 ft shoe with 10 ppg mud gives MAMW = 1,000 ÷ 208 + 10 = 14.81, rounded down to 14.8 ppg; with 11.5 ppg in the hole MAASP = (14.8 − 11.5) × 0.052 × 4,000 = 686 psi.
Formulas follow the IADC WellSharp field-unit formula sheet. Always use true vertical depth for pressure.
Summary
Drilling mud weight controls wellbore pressure: too light and formation fluid enters the well (a kick), too heavy and the formation fractures (lost circulation). This tool converts mud weight between pounds per gallon (ppg), pressure gradient (psi/ft and kPa/m), specific gravity, kg/L, kg/m³ and lb/ft³, gives hydrostatic pressure at a true vertical depth, Equivalent Circulating Density (ECD) from annular pressure loss, the kill mud weight and formation pressure from shut-in drill pipe pressure (SIDPP), the mud weight needed to balance a pore pressure, and the maximum allowable mud weight (MAMW) and MAASP from a leak-off test.
How it works
- Enter mud weight in any unit (ppg, psi/ft, SG, kg/L, kg/m³ or lb/ft³); the others update instantly.
- Hydrostatic pressure: P (psi) = MW (ppg) × 0.052 × TVD (ft). In metric, P (kPa) = SG × 9.80665 × TVD (m).
- ECD (ppg) = MW + annular pressure loss (psi) ÷ (0.052 × TVD ft).
- Kill mud weight (ppg) = MW + SIDPP ÷ (0.052 × TVD ft), rounded up to the next 0.1 ppg. Formation pressure = hydrostatic pressure + SIDPP.
- Required mud weight for a pore pressure = (pore pressure + overbalance) ÷ (0.052 × TVD).
- Maximum allowable mud weight = leak-off pressure ÷ (0.052 × shoe TVD) + test mud weight, rounded down; MAASP = (MAMW − current MW) × 0.052 × shoe TVD.
Use cases
- Convert a mud weight from ppg to SG, kg/m³ or psi/ft for a well plan or report.
- Calculate hydrostatic pressure at depth to check overbalance against pore pressure.
- Work out kill mud weight and formation pressure after shutting in on a kick.
- Compute ECD to check circulating pressure against the fracture gradient.
- Find the maximum mud weight and MAASP allowed by a casing-shoe leak-off test.
- Practise well-control calculations for IADC WellSharp or IWCF training.