Excavation & Earthwork Calculator
Dig volumes, swell, backfill and truckloads — trenches, pits and basements.
Excavation
Soil, backfill and disposal
Rates optional
By 1.5 m lift (IS 1200 Part 1 cl. 4.2.3)
| Lift | Depth | Volume (m³) | Share |
|---|
OSHA maximum allowable slopes (reference only)
- Stable rock — vertical (90°)
- Type A — ¾ : 1 (53°)
- Type A, short term (≤ 12 ft deep, ≤ 24 h) — ½ : 1 (63°)
- Type B — 1 : 1 (45°)
- Type C — 1½ : 1 (34°)
OSHA 29 CFR 1926 Subpart P, Appendix B, Table B-1, for excavations less than 20 ft (6.1 m) deep. Soil types are decided on site by a competent person. This calculator does not design sloping, benching or shoring.
Results are estimates from the formulas shown, not a professional design or certification. Have a qualified engineer verify anything safety-critical (structures, electrical installations, gas or pressure systems).
About the Excavation & Earthwork Calculator
Work out how much earth comes out of a trench, a group of footing pits or a basement, with vertical or sloped sides. Trenches use the trapezoidal section; pits and basements are prismoids, for which the prismoidal formula is exact — or enter three measured areas for an irregular dig. The volume is split into the 1.5 m lifts that IS 1200 measures, with its trench allowance and working space if you want them.
The in-place (bank) volume is then converted with the swell and compaction factors of US Army FM 5-434 for sand, common earth, clay or rock: how much loose soil you will handle, how much goes back as compacted backfill around the footings or pipes, how much is left to cart away, how many truckloads that is, and the cost. The OSHA maximum slopes are shown for reference — this is a quantity estimate, not a safety or shoring design.
How to use it
- Pick Trench, Pits / basement or By areas, and metric or US units.
- Enter the size at the bottom of the excavation, the depth and the side slope (horizontal per 1 vertical; 0 for vertical sides). For pits add the working space and the number of pits.
- Choose the soil for the swell and compaction factors, say whether the excavation is backfilled and how much volume the footings, pipes or structures take, and enter your truck size.
- Read the bank, loose, backfill and disposal volumes, the truckloads and the lifts; add rates for the cost, then copy or download the result.
Examples
20 × 0.6 × 1.2 = 14.4 m³ bank · common earth: × 1.25 = 18 m³ loose · 2 loads of a 10 m³ truck if all of it goes away
With the IS 1200 allowance for foundation trenches deeper than 1 m (50 mm per metre of depth each side) the width measured is 0.72 m and the volume 17.28 m³.
Bottom 3.0 × 2.7 = 8.1 m², middle 3.75 × 3.45 = 12.94 m², top 4.5 × 4.2 = 18.9 m² → 1.5 ÷ 6 × (8.1 + 4 × 12.94 + 18.9) = 19.69 m³ each · 78.75 m³ in total
3 ÷ 6 × (100 + 4 × 121 + 144) = 364 m³
13.9 m³ of compacted backfill needs 13.9 ÷ 0.90 = 15.44 m³ of bank soil — 1.04 m³ more than was dug, so nothing is left to cart away
Volumes
- Trench: V = length × (bottom width + s × depth) × depth, where s is the side slope (horizontal per 1 vertical) and the top width is bottom width + 2 s × depth.
- Pit or basement: a rectangular prismoid. V = depth ÷ 6 × (A bottom + 4 × A middle + A top), with each side moving out by s × depth from the bottom to the top. The prismoidal formula is exact for such shapes, which a simple average of the top and bottom areas is not.
- By areas: the same formula with areas you have measured, for example from levels or a survey.
The lift table splits the volume into 1.5 m stages from the ground, the way IS 1200 (Part 1) measures excavation, because rates rise with each extra lift.
Swell and compaction (FM 5-434 Table 1-1)
Earth bulks when dug and shrinks when compacted. From 1 m³ in the bank (in place): sand or gravel 1.11 m³ loose, 0.95 m³ compacted · loam (common earth) 1.25 loose, 0.90 compacted · clay 1.43 loose, 0.90 compacted · blasted rock 1.50 loose, 1.30 compacted. FM 5-434 notes these are averages and that soil weight and moisture change them; a test on your material is better.
Backfill space = excavation − the volume of footings, pipes or walls left in it. The bank soil needed is that space ÷ the compacted factor; the rest is surplus, carried away at the loose volume. Truckloads are the loose surplus ÷ the loose capacity of one load — check the truck's weight limit too, since wet clay or rock can reach it before the body is full.
Measurement to IS 1200 (Part 1)
Earthwork is measured in cubic metres of the authorised dimensions, without any allowance for bulking, to the nearest 0.01 m³ (cl. 2.3 and 4.1), in successive lifts of 1.5 m (cl. 4.2.3). Trenches up to 1.5 m wide and pits up to 10 m² on plan are "excavation in trenches"; anything wider and larger is "excavation over areas", or "surface excavation" in m² when 300 mm deep or less (cl. 4.6–4.8). For foundation trenches deeper than 1 m, 50 mm per metre of depth is added on each side of the specified width (cl. 4.8.2), and where working space is needed it is 600 mm from the face of the work (cl. 4.2.5.1).
OSHA maximum allowable slopes (reference only)
OSHA 29 CFR 1926 Subpart P, Appendix B, Table B-1 for excavations less than 20 ft deep: stable rock vertical (90°) · Type A ¾ : 1 (53°) — ½ : 1 (63°) for short-term excavations up to 12 ft deep · Type B 1 : 1 (45°) · Type C 1½ : 1 (34°). Soil types are classified by a competent person (Appendix A): Type A is cohesive soil of 1.5 tsf (144 kPa) unconfined compressive strength or more; Type C includes granular soils, submerged soil and soil with water seeping. Excavations 5 ft (1.52 m) or deeper need a protective system unless in stable rock (1926.652(a)), and sloping for excavations over 20 ft must be designed by a registered professional engineer.
Sources
- IS 1200 (Part 1):1992, Methods of Measurement of Building and Civil Engineering Works — Earthwork — archive.org
- US Army FM 5-434, Earthmoving Operations, Chapter 1, Tables 1-1 and 1-2 — GlobalSecurity.org copy
- OSHA 29 CFR 1926.652 and Subpart P, Appendices A and B — eCFR
Limitations
- This is a quantity estimate, not a professional design. It does not design or check sloping, benching, shoring or dewatering — follow your local regulations and a competent person or engineer on site.
- Swell and compaction factors are averages for each soil type; moisture, grading and the degree of compaction change them.
- Sloping ground, rock that needs blasting, stepped or benched sides and spoil left on site are not modelled; use the areas mode with measured sections for irregular ground.
- Truckloads are by volume only; check the payload of the truck for heavy soils.
Privacy
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Frequently asked questions
How do I calculate excavation volume for a trench?
Multiply the length by the average width and the depth. For vertical sides that is length × width × depth — 20 m × 0.6 m × 1.2 m = 14.4 m³. With sloped sides the top is wider by 2 × slope × depth; for a 1 m wide, 2 m deep trench with 1 : 1 sides the average width is 3 m, so 10 m of trench is 60 m³.
What is the swell factor of soil?
The extra volume soil takes up once dug. FM 5-434 gives bank-to-loose factors of 1.11 for sand and gravel, 1.25 for common earth (loam), 1.43 for clay and 1.50 for blasted rock — so 10 m³ of clay in the ground fills about 14.3 m³ of trucks.
Why is the prismoidal formula used for pits?
A pit with sloped sides is a prismoid, and V = d ÷ 6 × (bottom area + 4 × middle area + top area) gives its exact volume. Averaging only the top and bottom areas overestimates it; for the example pit the average-end-area method gives 20.25 m³ instead of 19.69 m³.
How many truckloads will I need?
Convert the soil you are carting away to loose volume and divide by what one truck carries. 14.4 m³ of common earth becomes 18 m³ loose — two loads of a 10 m³ tipper.
Why do I need more soil for backfill than the space I am filling?
Compacted soil is denser than it was in the ground for most soils: FM 5-434 gives 0.90 m³ compacted per m³ in the bank for common earth and clay, so filling 13.9 m³ takes 15.4 m³ of bank soil. Rock is the exception — it bulks even when compacted (1.30).
What slope should the sides of an excavation have?
That depends on the soil and the rules where you work, and it is a decision for a competent person on site. For reference, OSHA Table B-1 allows at most ¾ : 1 in Type A soil, 1 : 1 in Type B and 1½ : 1 in Type C for excavations under 20 ft, and requires a protective system from 5 ft deep unless in stable rock.