Excavation & Trench Calculator
Estimate dig volume for pads, footings, and trenches; convert in-place (bank) volume to hauled (loose) volume using soil-specific swell factors; and plan dump-truck loads and disposal cost. Supports rectangular excavations, vertical-wall trenches, and sloped-side trenches using the trapezoidal method. Formulas are documented below.
Excavation Shape
Hauling (optional)
Results
Loose volume to haul
– cubic yards
Call 811 before digging. Trenches 5 ft and deeper require OSHA cave-in protection - see the safety notes below.
The formulas this calculator uses
Loose volume = Bank × (1 + Swell%)
Truckloads = Loose ÷ capacity, rounded up
Worked example: 40 ft utility trench
- Trench: 40 ft long, 2 ft wide, 3 ft deep, mixed soil
- Bank volume: 40 × 2 × 3 = 240 ft³ = 8.9 yd³
- Loose volume: 8.9 × 1.25 = 11.1 yd³
- Hauling: one 12-yd³ tandem load - if weight allows; moist earth at ~2,500 lb/yd³ puts 11.1 yd³ near 14 tons, so plan two loads
Swell factors by soil type
| Material | Swell | Bank → loose multiplier | Loose weight (lb/yd³) |
|---|---|---|---|
| Sand | 10–15% | ×1.12 | 2,400–2,700 |
| Gravel | 10–15% | ×1.12 | 2,400–2,900 |
| Common earth (mixed) | 20–30% | ×1.25 | 2,000–2,500 |
| Clay | 25–40% | ×1.30 | 2,300–2,700 |
| Blasted rock | 40–60% | ×1.50 | 2,500–3,000 |
Common mistakes to avoid
Quoting haul-away from hole volume. A 10-yard basement dig produces 12–13 loose yards. Skips and trucks fill up faster than the hole empties.
Ignoring truck weight limits. Trucks are limited by payload weight as well as volume. Wet clay can hit a tandem's legal limit at 8–9 yards even though the bed holds 12.
Assuming excavated soil works as backfill. Organic topsoil and high-plasticity clay generally should not go back under slabs or footings. Budget for imported structural fill where it matters.
When to call a professional
Hire an excavation contractor - and where required, a geotechnical engineer - for digs deeper than 5 ft, work near foundations or pro
Assumptions used in this calculator
- Swell factors: sand/gravel 12%, mixed earth 25%, clay 30%, blasted rock 50%
- Sloped trench volume uses the trapezoidal average of top and bottom widths
- Truckloads rounded up by volume; payload weight may govern before volume
Change the adjustable inputs above where your project differs. Supplier figures and local codes govern; see our methodology.
Built for planning, not blind ordering. Verify dimensions, supplier conversions, local codes, and site conditions before construction.
Frequently Asked Questions
What is soil swell?
Undisturbed soil occupies less volume than the same soil after digging. Excavated clay expands about 30%, sand and gravel about 12%, and blasted rock up to 50%. Haul-away estimates must use the swelled (loose) volume, not the hole volume.
How many cubic yards of dirt fit in a dump truck?
A single-axle dump truck hauls about 5-6 cubic yards of soil; a tandem-axle truck hauls 10-14 cubic yards. Weight often governs before volume: moist earth at 2,200-2,700 lb per cubic yard can max out a truck's legal payload below its volumetric capacity.
How do I calculate trench volume?
Multiply trench width by depth by length, all in feet, then divide by 27 for cubic yards. For trenches with sloped sides, average the top and bottom widths before multiplying.
Do I need to call 811 before digging?
Yes. In the U.S., federal law requires calling 811 (or submitting online) at least a few business days before any excavation so utilities can mark buried lines. The service is free and skipping it risks injury, outages, and liability.
How deep can I dig without shoring?
OSHA requires cave-in protection (sloping, benching, shields, or shoring) for any trench 5 feet or deeper that workers will enter, and a competent-person inspection for anything deeper than 4 feet. Unstable soils can collapse at shallower depths - treat every trench wall as a hazard.