Excavation Slope & Shoring Calculator

Calculates the maximum allowable sloping angle, required horizontal offset, and top excavation width, per OSHA 29 CFR 1926 Subpart P, Appendix B (Sloping and Benching).

Critical safety context: Soil must be classified by a competent person per OSHA Appendix A before this table can be applied — the classification (Stable Rock, Type A, B, or C) depends on cohesion, moisture, prior disturbance, fissures, groundwater, vibration exposure, and other site-specific factors that only a qualified, trained person can assess in the field. This calculator only performs the arithmetic once that classification is known. Excavations 5 feet or deeper require a protective system (sloping, shoring, or shielding) unless entirely in stable rock. Excavations deeper than 20 feet require sloping/benching designed by a registered professional engineer — this tool's simplified tables do not apply beyond 20 feet.

Excavation Depth (ft)

Bottom Width of Excavation (ft)

Soil / Rock Classification (per OSHA Appendix A) Must be determined by a competent person, not assumed.

Short-term exposure (open ≤ 24 hours) — allows a steeper slope for Type A soil ≤ 12 ft deep

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Max. Allowable Slope

0 ft

Horizontal Offset (each side)

0 ft

Top Width of Excavation

Formula Reference

Horizontal Offset (per side) = Depth × Slope Ratio (H:V)
Top Width = Bottom Width + (2 × Horizontal Offset)
Minimum spoil pile / equipment setback from excavation edge = 2 feet (OSHA 1926.651(j)(2))

OSHA Maximum Allowable Slopes (Appendix B, Table B-1)

Stable Rock	Vertical — 90°
Type A	3/4H:1V — 53°
Type A (short-term, ≤ 12 ft depth)	1/2H:1V — 63°
Type B	1H:1V — 45°
Type C	1½H:1V — 34°

Depths greater than 12 feet do not qualify for the Type A short-term exception even for short-term exposure — the standard 3/4H:1V slope applies instead.

Based on OSHA 29 CFR 1926 Subpart P, Appendix B (Sloping and Benching). This tool covers simple sloping only — it does not cover benching configurations, shoring/shield tabulated data (Appendices C and D), layered soil profiles, or surcharge load reductions (which require a further slope reduction per a competent person's judgment). It does not replace a competent person's on-site soil classification or a registered professional engineer's design for excavations over 20 feet deep. For customized calculators tailored to your organization, please contact Impact Tech Solutions.