Backfill Calculator
A 40 foot trench, 2 feet wide and 2 feet deep, is 5.93 cubic yards and 6.99 short tons at 1,400 kg/m³.
Last updated . These backfill tools start at 1,400 kg/m³, about 1.18 US tons per cubic yard and 1.07 tonnes. Depth starts in inches, so a 2 foot trench is 24 inches, or switch the depth menu to feet and type 2.
Calculate backfill for trenches and foundations. Choose your shape below. Swell and the split between native soil and bedding are the trench calculator.
Building a block wall? Our guide to retaining wall blocks covers block types, setback and the drainage stone behind them.
Backfill – Straight Trench
Width
Calculation is based on average density of 1400 kg/m³.
Calculation Results
Gravel Volume
0.00 m³
Gravel Weight
0.00 t
Cubic yards
0.00 yd³
Cubic meters
0.00 m³
Tons (2,000 lb)
0.00 tons
Tonnes (1,000 kg)
0.00 t
Bags (0.5 ft³)
0
Converted from the volume and density already used above. Tons are US short tons. Tonnes are metric tonnes, the same unit as the “t” menu. Bags are 0.5 cubic foot retail bags, rounded up.
Advertisement
Backfill – Curved Trench
Calculation is based on average density of 1400 kg/m³.
Calculation Results
Gravel Volume
0.00 m³
Gravel Weight
0.00 t
Cubic yards
0.00 yd³
Cubic meters
0.00 m³
Tons (2,000 lb)
0.00 tons
Tonnes (1,000 kg)
0.00 t
Bags (0.5 ft³)
0
Converted from the volume and density already used above. Tons are US short tons. Tonnes are metric tonnes, the same unit as the “t” menu. Bags are 0.5 cubic foot retail bags, rounded up.
Advertisement
Rectangular Backfill Calculator
Calculation is based on average density of 1400 kg/m³.
Calculation Results
Gravel Volume
0.00 m³
Gravel Weight
0.00 t
Cubic yards
0.00 yd³
Cubic meters
0.00 m³
Tons (2,000 lb)
0.00 tons
Tonnes (1,000 kg)
0.00 t
Bags (0.5 ft³)
0
Converted from the volume and density already used above. Tons are US short tons. Tonnes are metric tonnes, the same unit as the “t” menu. Bags are 0.5 cubic foot retail bags, rounded up.
Advertisement
What Is Backfill Material?
Backfill refers to material placed back into an excavation after construction work such as foundations, trenches, or underground utilities. It restores ground level, provides structural support, and ensures proper drainage around built elements.
The type of backfill used depends on the application. Soil backfill is common for general fill, while gravel or crushed stone is preferred where drainage and load stability are critical.
Common Types of Backfill Materials
| Material | Typical Density (kg/m³) | Best Use |
|---|---|---|
| Excavated soil | 1,200 – 1,600 | General fill, landscaping |
| Compacted clay | 1,500 – 1,800 | Structural fill, embankments |
| Sand | 1,500 – 1,700 | Pipe bedding, leveling |
| Gravel / crushed stone | 1,600 – 2,000 | Drainage and foundation support |
| Flowable fill (CLSM) | 1,800 – 2,200 | Controlled low-strength fill |
How Backfill Volume Is Calculated
Backfill volume is calculated based on the excavation size and depth:
Volume = Length × Width × Depth
For trenches, width may vary depending on pipe diameter or excavation slope. The calculators above allow both fixed and variable widths to reflect real trench conditions.
Backfill for Trenches vs Foundations
| Application | Material | Key Requirement |
|---|---|---|
| Utility trenches | Sand or gravel | Proper compaction and pipe protection |
| Foundation walls | Granular fill | Drainage and reduced pressure |
| Slab backfill | Compacted soil or sand | Uniform support |
| Retaining walls | Gravel | Drainage to relieve hydrostatic pressure |
Compaction and Settlement Considerations
Backfill material must be compacted in layers to prevent future settlement. Loose fill can settle over time, leading to surface depressions, structural instability, or damage to foundations and utilities.
Typical compaction practices:
- Compact in layers of 6″–12″ thickness
- Use mechanical compaction for structural areas
- Add 5–15% extra material to account for compaction loss
Drainage and Backfill Selection
Drainage is a critical factor when selecting backfill material. Poor drainage can lead to water buildup and pressure against structures.
- Use gravel backfill for drainage-critical areas
- Install perforated pipes where water accumulation is expected
- Avoid clay soils near foundations due to water retention
Common Backfill Mistakes
- Using unsuitable soil with high moisture content
- Failing to compact in layers
- Ignoring drainage requirements near structures
- Overfilling without accounting for settlement
FAQs
What is the best material for backfill?
It depends on the application. Gravel is best for drainage, while compacted soil works for general fill. Sand is commonly used around pipes and utilities.
How much extra backfill should I order?
Add 5–15% extra material to account for compaction and settlement after installation.
Do I need to compact backfill?
Yes. Proper compaction is essential to prevent settling and ensure long-term stability.
Can I reuse excavated soil as backfill?
Yes, if the soil is suitable and free of debris. However, granular materials are preferred for structural and drainage applications.
How much backfill do I need for a 40 foot trench?
Two feet wide and two feet deep along 40 feet is 5.93 cubic yards. With the depth left in inches, type 24. At 1,400 kg/m³ the order line reads 4.53 cubic meters, 6.99 short tons, 6.34 tonnes, and 320 bags of 0.5 cubic feet. That is the hole, not a compacted-in-place discount.
How many bags of backfill are in a cubic yard?
One cubic yard is 54 bags of 0.5 cubic feet. The 40 foot trench is 160 cubic feet, so the bag line reads 320. At 1.18 tons per yard a cubic yard is about 2,360 pounds, roughly 48 bags of 50 pounds. A trench this size is a bulk load.
How much does a yard of backfill weigh?
At the 1,400 kg/m³ starting density a cubic yard is 1.18 short tons and 1.07 tonnes. Washed gravel is usually heavier, near 1.35 to 1.43 tons, and it belongs on a gravel page. Wet clay backfill can also climb past 1.18 tons. Use the ticket if you have one.
How much backfill for a foundation wall?
A wall 30 feet long with a 2 foot gap filled 3 feet deep is 30 × 2 × 36 ÷ 324 = 6.67 cubic yards, about 7.86 short tons at 1,400 kg/m³. Type 36 inches or switch depth to feet and type 3. The trench example and the wall example are different boxes.
Does backfill volume include compaction?
No. 5.93 cubic yards is the space in the trench. The compaction note already on this page is why people order extra. The calculator does not hide 10 percent inside the result. Add it when you call the supplier.
Can I use the excavated soil as the backfill number?
Only if that soil is what you will put back, which the existing question above already flags. The 6.99 ton figure is for material at 1,400 kg/m³ placed in the 40 foot box. Rock, roots, and a wet spoil pile will not match that weight even when the hole is the same size.
Backfill quantities at 1,400 kg/m³
A 2 foot depth is 24 inches while the depth menu stays on inches. Tons use 1.18 short tons per cubic yard.
| Trench | Depth typed | Cubic yards | Short tons |
|---|---|---|---|
| 40 ft × 2 ft | 24 in (2 ft) | 5.93 | 6.99 |
| 30 ft × 2 ft | 36 in (3 ft) | 6.67 | 7.86 |
| 20 ft × 1 ft | 12 in | 0.74 | 0.87 |
Worked example
Enter 40 feet long, 2 feet wide, and 24 inches deep on the straight trench tool. Leave 1,400 kg/m³. The order line reads 5.93 cubic yards, 4.53 cubic meters, 6.99 short tons, and 6.34 tonnes.