SPT Correlations
Correct field SPT N to N60 and (N1)60 and estimate friction angle, relative density, undrained strength, Es and allowable bearing pressure.
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About this test
Enter the field N value, hammer energy, depth and overburden pressure. Results use widely published correlations, each named in the formula list — useful for preliminary design, theses and checking reports.
How it's calculated
- N60 = N × Er/60 × CR
- (N1)60 = N60 × √(100/σ′v) ≤ 1.7 N60
- φ′ = √(20 (N1)60) + 20 (Hatanaka & Uchida)
- Dr = √((N1)60/60) (Skempton)
- cu ≈ 5 × N60 kPa (Stroud)
- qa (25 mm) — Meyerhof as modified by Bowles
Results are calculated from the values you enter using standard formulas. Download the PDF to keep a record. For certified testing, design or construction, talk to our engineers.
Kataria Engineering & Consultancy Services (2026). SPT Correlations [online calculator]. https://katariaengineering.com/tools/spt-correlations-calculator.html
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