ToolsStructuralPipes & Casing

Hoop Stress Calculator

Calculate hoop, axial, and Von Mises stress in pressurised pipes and casings. Thin-wall formula with optional FoS check against yield strength.

Last updated 25 August 2026

About this tool

Calculate hoop (circumferential), axial, and Von Mises stress in a pressurised thin-walled pipe or casing. Enter internal pressure, outer diameter, and wall thickness.

Optionally enter the yield strength to check the factor of safety against yielding. Includes a thin-wall validity check (d/t > 20) and warns when thick-wall equations (Lamé) should be used instead.

Used for drilling casing design, pipeline engineering, pressure vessel checks, and water/gas main assessment. Material presets include common steel grades (S235, S355, API 5CT L80).

How to use this tool

1. Enter internal pressure, outer diameter, and wall thickness — in MPa and mm.

2. Optionally enter yield strength — to calculate FoS against yielding.

3. Read the three stress components and Von Mises equivalent — hoop stress is always the largest for internal pressure.

Technical information

σh = p × d / (2 × t) — hoop stress (thin-wall)

σa = p × d / (4 × t) — axial stress (closed ends)

σvm = √(σh² − σh·σa + σa²) — Von Mises equivalent stress

Uses mean diameter (OD − t). Thin-wall approximation valid for d/t > 20. For thick-walled pipes, use Lamé equations.

Limitations

Thin-wall formula only. For d/t < 20 (thick-walled pipes and heavy casings), the stress distribution across the wall is non-uniform and Lamé equations should be used.

Assumes internal pressure only. External pressure (e.g. collapse loading on casing) requires a separate analysis. Does not account for bending, thermal, or installation stresses.

Corrosion allowance is not included. Reduce the wall thickness by the expected corrosion loss before calculating stress for in-service assessment.

Revision history

25 August 2026: Initial release

Disclaimer

This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.

Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.

All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.

By using this tool, you accept full responsibility for how you interpret and apply the information provided.

Spotted an error? Let us know.

Internal pressure (MPa)

Outer diameter (mm)

Wall thickness (mm)

Yield strength (MPa) — optional

Enter to calculate FoS against yield. S235 = 235, S355 = 355, API 5CT L80 = 552 MPa.