Backfill quantity Calculator: measuring notes and method
Measure the space being refilled
Enter the void that remains after foundations, pipes or other permanent work. If the space cannot be represented by one rectangle, save several separate entries and total their volumes.
Match density to the volume
Ask the supplier whether their density represents loose or placed material. Keep any documented compaction conversion separate from an allowance for handling losses.
Formula
Volume = length × width × depth × (1 + waste ÷ 100). Mass = volume × density.
Worked examples in metric and imperial units
Illustrative values match Reset example and stay fixed when you edit the calculator. Both columns describe the same calculation; converted inputs are rounded.
Metric worked example
- Length
- 6 m
- Width
- 4 m
- Finished depth
- 300 mm
- Bulk density
- 1,700 kg/m³
- Waste allowance
- 10 %
Material weight: 13,464 kg
Imperial worked example
- Length
- 19.685 ft
- Width
- 13.1234 ft
- Finished depth
- 11.811 in
- Bulk density
- 106.1275 lb/ft³
- Waste allowance
- 10 %
Material weight: 29,683.039 lb
Follow the calculation
Lengths in this working are in metres.
- Net volume = 6 × 4 × 0.3 = 7.2 m³.
- Allowance multiplier = 1 + 10 ÷ 100 = 1.1.
- Mass = 7.92 m³ × 1,700 kg/m³ = 13,464 kg.
Unit conversions
1 m³ = 1,000 L ≈ 1.30795 yd³. One cubic yard is 27 ft³.
For metric tonnes, divide kg by 1,000. For US short tons, divide lb by 2,000; a long ton is 2,240 lb. Confirm your supplier’s unit.
Reviewed 19 October 2026. How calculations are checked · Report a correction