Excavation & Soil Volume Calculator
Calculate foundation trench earthwork volume, soil bulking / swell factor, dumper truckloads needed, and excavation costs.
Trench / Pit Dimensions
Truck Capacity & Costs
6,000 CFT (170 m³)
Complete Guide to Foundation Excavation & Earthwork Calculation
Excavation is the first physical step in constructing building foundations, basements, septic tanks, and swimming pools. Estimating exact bank cubic yards / cubic feet (in-situ solid ground) versus loose excavated volume is vital for logistics planning and hiring dumper trucks.
Earthwork Formulas
- In-Situ Bank Volume (CFT) = Pit Length × Width × Depth
- Cubic Meters (m³) = Total CFT ÷ 35.3147
- Loose Soil Volume = In-Situ Volume × Soil Swell Factor
- Truck Trips Required = Math.ceil(Loose Volume ÷ Truck Capacity)
- Total Earthwork Budget = (In-Situ CFT × Rate/CFT) + (Trips × Trip Rate)
Soil Bulking & Swell Factors
- Sand & Loose Gravel: 1.10 - 1.15 (10% to 15% volume expansion)
- Common Earth / Topsoil: 1.20 - 1.25 (20% to 25% volume expansion)
- Dense Clay Soil: 1.30 - 1.35 (30% to 35% volume expansion)
- Blasted Rock / Boulder: 1.50 - 1.60 (50% to 60% volume expansion)
Frequently Asked Questions (FAQs)
What is the difference between In-Situ (Bank) Volume and Loose Volume?
In-situ (Bank) volume is the compacted, undisturbed earth measured in the ground before digging. When soil is excavated, air pockets enter the soil structure, increasing its volume by 15% to 35% (Loose volume). Dumper truck capacity must always be calculated against loose volume.
Is it cheaper to hire a JCB per hour or pay per CFT?
For open residential plots with easy truck access, hourly JCB hiring (typically ₹1,000 to ₹1,400/hour in India) is usually cheaper if dumper trucks are readily lined up. For congested urban areas or deep rocky trenches, per-CFT contract rates (₹10 to ₹18/CFT) provide financial safety against equipment breakdown delays.
How much excavated soil should be retained for backfilling?
Approximately 25% to 35% of the excavated soil should be retained on site for backfilling around foundation footings, plinth beam cavities, and sub-base leveling after concrete cures.