Point Load Strength Index Calculator (Is50)

Calculate the point load strength index Is50 from field and laboratory point load tests and correlate to uniaxial compressive strength (UCS) per ASTM D5731 and ISRM standards.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)
σy — Normal Stress Y (MPa)
τxy — Shear Stress (MPa)
⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.
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How It Works

Calculate the point load strength index Is50 from field and laboratory point load tests and correlate to uniaxial compressive strength (UCS) per ASTM D5731 and ISRM standards

Each component has a specific meaning:

  • Field — The field recorded for the patient or scenario being assessed.
  • Laboratory point load tests — The laboratory point load tests recorded for the patient or scenario being assessed.
  • Correlate — The correlate recorded for the patient or scenario being assessed.

Note: Interpret the point load strength index result against the clinical thresholds and context described above.

How to Use

Enter the field, laboratory point load tests, correlate for the patient or scenario you are assessing. Calculate the point load strength index Is50 from field and laboratory point load tests and correlate to uniaxial compressive strength (UCS) per ASTM D5731 and ISRM standards. Use the point load strength index result to inform your clinical assessment.

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Frequently Asked Questions