Backfill Calculator
Estimate backfill material needed for an excavation.
Last updated 2026-08-21
What Is a Backfill Calculator?
A backfill calculator tells you how much material you need to refill a hole after the structure, pipe, or foundation is in place. It subtracts the structure volume from the excavation volume and then adds a compaction factor. This is the number you order from a supplier to reach the finished grade.
How It Works
Net volume = Excavation − Structure. Backfill = Net × (1 + Compaction ÷ 100).
Example
100 cu yd excavation with 40 cu yd of structure at 10% compaction: 60 × 1.1 = 66 cu yd.
How to Calculate
- Enter the total excavation volume in cubic yards. For a 100 cubic yard hole, that is the starting point.
- Enter the structure volume, which is the part of the hole filled by the foundation, pipe, or wall. Say it is 40 cubic yards.
- The tool subtracts to find the net backfill, which is 60 cubic yards.
- Add a compaction factor, typically 10 to 20%, because compacted fill settles to a smaller volume.
- At a 10% factor, 60 cubic yards becomes 66 cubic yards of material to order.
Typical Compaction Factors by Material
| Backfill Material | Compaction Factor |
|---|---|
| Crushed stone / gravel | 5 to 10% |
| Sand | 8 to 12% |
| Sandy loam | 10 to 15% |
| Clay | 15 to 25% |
| Topsoil (final grade) | 10 to 15% |
Sources
Frequently Asked Questions
What is the structure volume?
The volume of the foundation, pipe, or wall that fills part of the hole and will not need backfill.
Why a compaction factor?
Backfill compacts to a smaller volume, so you order extra to end up at the desired grade.
What is a typical compaction factor?
10–20% is common, depending on the material and how much it is compacted.
Estimate the cost with the Excavation Cost Calculator or browse Excavation Calculators