The space removed from the ground, the loose spoil on a vehicle and the space left around a foundation are not interchangeable. The Whatson Excavation & Backfill Calculator separates them.
It starts with a schedule of rectangular pits. Each row has length, width, depth and the count of identical pits, using the selected unit. Irregular trenches or stepped excavations need to be divided into suitable measured sections.
Retained volume means occupied space
The permanently occupied volume is entered in m³, regardless of the pit measurement unit. It represents concrete or other permanent construction occupying part of the excavated space.
It is not the quantity of excavated soil you plan to keep on site. The calculator subtracts it from excavation volume to find the final space that may require backfill.
Keeping spoil for reuse is a separate site decision. This model does not automatically subtract reusable soil from delivered fill or net off the transport trips.
Follow one pit through the outputs
Use a pit 10 × 5 × 3 ft, quantity 1, zero permanently occupied volume, swell factor 1.2, delivered fill factor 1.15 and a 300 cft truck.
The checked excavation volume is 150 cft, approximately 4.25 m³. Loose spoil becomes 180 cft, giving one truck trip. Final backfill space remains 150 cft in this zero occupied volume example, and the delivered fill estimate is 172.5 cft.
In a real foundation, enter the permanent occupied volume. Leaving it at zero would treat the entire pit as space to fill again.
Use the factors for different stages
The swell factor applies to excavated spoil. The fill factor applies to the final backfill space. They are adjustable estimating assumptions, not automatic soil classifications.
A wet soil, mixed debris or different fill material may require a different approach. Obtain quantities and factors appropriate to the actual work instead of assuming the defaults describe the site.
What the cost includes
Excavation is priced in PKR per m³ of in situ excavation. Fill is priced in PKR per cft of delivered fill. The entered total combines those two charges.
There is no spoil disposal or haulage rate in this tool. The trip count is a quantity aid, not a priced transport line. Dewatering, support, access restrictions and labour outside the quoted scope also need separate budget items.
Excavation dimensions and support arrangements must come from the project requirements. This calculator does not assess safe digging or soil stability. Use its schedule to document an already specified quantity, then keep the pit references with the exported result.