Pile Group Efficiency Calculator

Converse-Labarre group efficiency for a pile block.

RowsColumnsPile diameter (mm)Centre spacing (mm)Usually 2.5–3.5 D

Group efficiency (%)

Spacing / diameter

Friction piles in clay shade each other — a 3×3 group at 3D delivers ~75% of nine solo piles. End-bearing piles on rock ignore the formula and keep ~100%.

Formula

η = 1 − θ/90 · [(n−1)m + (m−1)n]/(mn), θ = atan(D/s)

References: Converse-Labarre; IS 2911 group provisions

Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.

Pile Group Efficiency Calculator is a free pile group efficiency for geotechnical engineers and foundation designers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.

About Pile Group Efficiency Calculator

Converse-Labarre group efficiency for a pile block. The calculation implements η = 1 − θ/90 · [(n−1)m + (m−1)n]/(mn), θ = atan(D/s) (Converse-Labarre; IS 2911 group provisions). Friction piles in clay shade each other — a 3×3 group at 3D delivers ~75% of nine solo piles. End-bearing piles on rock ignore the formula and keep ~100%.

How to use Pile Group Efficiency Calculator

1Enter Rows.
2Enter Columns.
3Enter Pile diameter in mm.
4Enter Centre spacing in mm (Usually 2.5–3.5 D).
5Read Group efficiency, Spacing / diameter instantly — no submit button needed.
6Need US units? Flip the SI/Imperial toggle and every field converts.

Why use Pile Group Efficiency Calculator?

✓Implements the standard formula — η = 1 − θ/90 · [(n−1)m + (m−1)n]/(mn), θ = atan(D/s)
✓Reference cited on-page: Converse-Labarre; IS 2911 group provisions
✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
✓Live worked example: the substitution recomputes from your numbers
✓Runs entirely in your browser — nothing uploaded, free forever

Frequently asked questions

What formula does the Pile Group Efficiency Calculator use?+

It computes η = 1 − θ/90 · [(n−1)m + (m−1)n]/(mn), θ = atan(D/s), per Converse-Labarre; IS 2911 group provisions. The formula is displayed under the result along with a worked example substituted with your own inputs.

What should I keep in mind when using this calculator?+

Friction piles in clay shade each other — a 3×3 group at 3D delivers ~75% of nine solo piles. End-bearing piles on rock ignore the formula and keep ~100%.

Can this replace a soil investigation?+

No calculator replaces boreholes and lab tests — but with investigated parameters in hand, this gives you the standard-method result instantly, with the formula shown so reviewers can check it.

Is the Pile Group Efficiency Calculator free to use?+

Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.

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