Work out how much soil to dig for footing pits, wall trenches or a basement before you hire a machine. Enter the sizes in metres or feet, and the calculator gives the volume in m³ and cu ft, the loose volume after bulking, the soil left for refilling and the number of lorry or tractor trips. Part of our quantity surveying tools.
How to use the excavation calculator
- Choose Footing pits, Trenches or Open area, and metres or feet.
- Enter the sizes. For footing pits, enter each footing size, the pit depth and the number of pits. Add a row for each different size.
- Set the working space on each side and the side slope.
- Choose the soil type, which sets the bulking factor.
- Enter how much soil you will keep on site for refilling, and the size of the vehicle.
- Add digging and carting rates if you want a cost, then download the result as CSV, print it or share a link.
Excavation Quantity Calculator
How much soil to dig for footing pits, trenches or a basement, how much it bulks up, and how many trips to cart it away
Machine output and rates
Quantity by item
Where the soil goes
Checks
Planning estimate. Actual quantities depend on the soil, groundwater and site. Deep excavation, or digging near a boundary, road or neighbouring building, can collapse without warning: get an engineer's advice and follow IS 3764 on site. This tool does not design shoring or check soil stability.
Formulas used
| Item | Formula |
|---|---|
| Bottom of the pit | Footing length + 2 × working space, by footing width + 2 × working space |
| Top of the pit | Bottom size + 2 × slope × depth on each side |
| Pit or open area with sloping sides | V = D ÷ 6 × (A1 + A2 + 4 × Am), where A1 is the bottom area, A2 the top area and Am the area at mid-depth |
| Pit with straight sides | V = length × width × depth |
| Trench | V = (bottom width + top width) ÷ 2 × depth × length |
| Loose volume | Volume in the ground × bulking factor |
| Trips | Loose volume carted away ÷ vehicle capacity, rounded up |
| Excavator time | Volume ÷ output per hour (30 m³ per hour by default) |
| Cubic feet | m³ × 35.3147 |
Worked example
Eight footings of 1.5 × 1.5 m in ordinary soil, each in a pit 1.5 m deep with straight sides and 0.3 m working space, all the soil carted away in an 8 m³ lorry:
- Pit size: 1.5 + 2 × 0.3 = 2.1 m each way.
- Volume of one pit: 2.1 × 2.1 × 1.5 = 6.62 m³. For eight pits: 52.92 m³, or about 1,869 cu ft.
- Loose volume at 1.25: 66.15 m³.
- Trips: 66.15 ÷ 8 = 8.27, rounded up to 9 trips.
- Excavator time at 30 m³ per hour: about 1.8 hours of digging, before moving between pits.
If half the soil stays on site for refilling, only 33.08 m³ of loose soil leaves the site, which is 5 trips.
Frequently asked questions
How is excavation quantity calculated?
For straight sides, volume = length × width × depth of the pit, where length and width include the working space on each side. A 1.5 × 1.5 m footing with 0.3 m working space and 1.5 m depth needs a 2.1 × 2.1 m pit, which is 6.62 m³. With sloping sides the top of the pit is wider, and the calculator allows for that.
What is the bulking factor of soil?
Soil takes up more space once it is dug. The bulking factor is loose volume ÷ volume in the ground. Common planning figures are about 1.15 for sand, 1.25 for ordinary soil, 1.35 for clay and 1.65 for blasted rock. The real figure depends on the soil and its moisture.
How do I work out the number of lorry or tractor trips?
Number of trips = loose volume to be carted away ÷ capacity of the vehicle, rounded up. For 52.92 m³ in the ground with a bulking factor of 1.25, the loose volume is 66.15 m³, which is 9 trips in an 8 m³ lorry.
How much working space should I leave around a footing?
Leave enough room to fix formwork and work around the footing. This calculator starts at 0.3 m on each side, which you can change to match your drawing, your contract’s measurement rule or the conditions on site.
When does an excavation need shoring?
IS 3764 says trenches in soil more than 1.5 m deep must be securely shored and timbered. This does not apply where the sides are sloped to within 1.5 m of the bottom, provided the person in charge has inspected the slope and certified it as stable.
How far from the edge should dug soil be kept?
IS 3764 asks for a clear strip between the edge of the trench and the excavated material, at least one third of the final depth and never less than 1 m, or more if the design requires it.
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Disclaimer: Online educational publication only. Not a substitute for geotechnical advice, shoring design or site supervision by a qualified engineer. Full disclaimer · contact@speakarch.com
Last updated: 9 November 2026