Pipeline Maximum Pressure Calculator

Calculator Inputs

Length unit

Stress unit

Method selection

Outside diameter

Use outside diameter (OD).

Nominal wall thickness

Nominal thickness before allowances.

Corrosion allowance

Subtracted from thickness.

Mill tolerance (%)

Typical values: 10–12.5%.

Weld efficiency (E)

Range 0.5 to 1.0.

Design factor (F)

Often based on location class.

Temperature factor (T)

Derating at elevated temperatures.

Thin-wall limit (t/D)

Auto switches above this threshold.

Stress input mode

Choose how allowable stress is defined.

Allowable stress

Used when mode is “Allowable stress”.

SMYS

Used when mode is “SMYS with safety factor”.

Safety factor

Allowable = SMYS / safety factor.

Effective thickness = (t_nom × (1 − mill_tolerance)) − corrosion_allowance.

Example Data Table

Scenario	OD (mm)	t_nom (mm)	CA (mm)	S_allow (MPa)	E	F	T	Recommended Pmax (MPa)
Steel water line	273	9.27	1.00	200	1.00	0.72	1.00	~10.3
Higher design factor	219	8.18	1.00	190	1.00	0.80	1.00	~10.1
Elevated temperature	323.9	10.31	1.50	210	0.95	0.72	0.85	~9.0

Values are illustrative for learning and checks. Always align factors with project requirements.

Formula Used

1) Effective thickness

t_eff = (t_nom × (1 − Tol%/100)) − CA

Tol% is the mill tolerance; CA is corrosion allowance.

2) Thin-wall (Barlow) estimate

P = (2 × S_allow × t_eff × E × F × T) / D

P in MPa when S is MPa and lengths are consistent.

3) Thick-wall (Lamé) estimate

P = S_allow × (r_o² − r_i²) / (r_i² + r_o²) × E × F × T

Uses maximum hoop stress at the inner wall for a closed-end cylinder screening check.

How to Use This Calculator

Select length and stress units that match your data.
Enter outside diameter and nominal wall thickness from the pipe schedule.
Set corrosion allowance and mill tolerance to reflect expected reductions.
Choose how you define allowable stress, then enter stress values.
Enter weld efficiency, design factor, and temperature factor for your service.
Use Auto for quick screening; override method if needed.
Press Calculate to view results, then export CSV or PDF.