Plan the soil to dig out and take away
Depth determines the size of the excavation. Disposal also depends on how much space the loosened soil takes up and the weight your carrier accepts.
How much soil for a 20 m² terrace?
Multiply area by depth in metres. Removing 25 cm from a 5 × 4 m area gives 20 × 0.25 = 5 m³ of soil in place. For an irregular outline, the calculator uses your plan’s actual area.
The 25 cm depth is an example, not a construction recommendation. Finished levels, ground and planned layers determine the depth. Calculate sections separately if their depths differ.
In-place volume (m³) = area (m²) × depth (cm) ÷ 100
Why does dug-out soil take up more space?
Digging loosens the ground. The same soil may occupy more space in a skip: this is bulking, or swell. An assumed 25% increase turns our 5 m³ into 6.25 m³ to remove.
Use a factor suited to the actual ground, not a universal percentage. Bulking increases the estimated volume; it does not automatically increase the soil’s weight.
Loose volume = in-place volume × (1 + bulking percentage ÷ 100)
Check both skip capacity and payload
The engine calculates weight from the density of soil in place. At an assumed 1.5 t/m³, 5 m³ weighs 7.5 tonnes. The density, bulking and skip capacities here are example inputs to replace with site and carrier information.
Both results are rounded up, then the larger count is used. A skip can reach its payload limit before it looks full. Confirm its permitted load as well as its cubic capacity.
| Limit per skip | Calculation | Skips |
|---|---|---|
| 8 m³ | 6.25 ÷ 8 | 1 |
| 6 tonnes | 7.5 ÷ 6 | 2 |
| Count used | Higher requirement | 2 |
Ask for a complete disposal quote
Skip count alone is not a project price. Check delivery, collection, hire duration, soil disposal charges, accepted materials and vehicle access.
If some soil stays on site, estimate the amount actually removed separately. This calculation assumes all excavated soil is taken away. It does not assess ground stability or excavation safety.
Keep the same plan for the next layer
Use the project continuation links for geotextile or gravel. Only the missing roll, depth or material details need adding. Saving to My projects keeps your excavation depth on this device.
If the shape changes, reopen affected calculations and confirm the revised quantities. The gravel volume added is not necessarily the same as the soil volume removed.
Mistakes to avoid
- Entering 25 metres instead of 25 centimetres.
- Applying bulking to the calculated weight.
- Choosing a skip only by cubic capacity.
- Treating an example depth as a building rule.
Before you start digging
How deep should I excavate for a terrace?
The tool calculates the depth you enter; it does not choose it. Confirm the proposed layers, levels and supporting ground before digging.
Which soil density should I enter?
Weight uses the volume before excavation. Enter the density of soil in place, not the density of an already loosened pile.
Why two skips when the volume fits into one?
The weight limit may be reached first. The calculation keeps the higher count rather than assuming an overloaded skip.
Can I reuse a saved L-shaped terrace?
Yes. Select the project zone or follow the link from the terrace result. Its outline and area are reused; add the depth and disposal details.
Understanding volume changes
FHWA distinguishes in-place, loose and compacted material. Its values are not prescriptions for your ground; the figures above are calculation examples. FHWA — Earthwork Design