Trench & Excavation Calculator
Volume, spoils, backfill & safety — everything you need for trench planning
| Material | Swell Factor | Density (ton/CY) | Spoils Weight | Net Haul Weight |
|---|
| # | Label | Length (ft) | Width (ft) | Depth (ft) | Volume (CY) | Spoils (CY) |
|---|
| Depth | Requirement | Notes |
|---|---|---|
| 0 – 5 ft | Inspect daily; shoring may not be required for competent soil | Competent person must evaluate site conditions |
| 5 – 20 ft | Benching, sloping, shoring, or trench box required | Method depends on soil classification |
| > 20 ft | Engineered shoring system required | Must be designed by a registered PE |
| Soil Type | Description | Max Slope (H:V) | Allowed Methods |
|---|---|---|---|
| Type A | Cohesive soils, unconfined compressive strength ≥1.5 tsf. Includes hard clays, cemented soils. | 0.75:1 (53°) | Sloping, benching, shoring, shield |
| Type B | Cohesive soil, 0.5–1.5 tsf. Granular cohesionless soils, fissured or layered soils. | 1:1 (45°) | Sloping, shoring, shield |
| Type C | Cohesive soil <0.5 tsf. Granular soils (gravel, sand, loamy sand), submerged soil, sloped layers. | 1.5:1 (34°) | Sloping, shoring, shield |
Cutting back the trench wall at an angle. Least expensive but requires more space and excavation. Angle depends on soil type (Type A: 0.75:1, Type B: 1:1, Type C: 1.5:1).
Cutting horizontal steps into the trench wall. Only allowed in Type A and Type B soils. Not permitted in Type C soils or in hard rock.
Installing supports (timber, hydraulic, or pneumatic) against trench walls. Hydraulic shores are most common — contact the manufacturer for load ratings.
Prefabricated steel box placed in the trench to protect workers. Does not prevent cave-in — moves with excavation. Rated for specific soil loads by the manufacturer.
Egress requirements
For trenches 4 ft or deeper, a safe means of egress (ladder, steps, ramp) must be provided within 25 ft of workers. Ladders must extend 3 ft above the trench lip.
Spoil pile setback
Spoil piles must be placed a minimum of 2 ft from the trench edge. Greater setback is required for deep trenches to prevent surcharge loading on the trench walls.
Underground utilities
Call 811 (USA) before you dig. All underground utility lines must be located and protected before excavation begins. Hand-dig within 18–24 in of marked utilities.
Water accumulation
Workers must not work in trenches with accumulated water unless adequate precautions are taken (dewatering, support systems). Water weakens trench walls significantly.
Atmospheric hazards
Trenches 4 ft or deeper must be tested for hazardous atmospheres (oxygen deficiency, toxic gases, flammable vapors). Confined space entry procedures may apply.
This reference is for general guidance only. Always consult OSHA 29 CFR 1926.650-652 and employ a competent person on-site. Regulations may vary by jurisdiction.