Backfill Calculator
Enter your excavation’s footprint and backfill band width, pick a project type or custom depth, and choose a material to see the tons you need.
Measure straight across the widest point.
Adjust depth below if needed.
Covers spillage and compaction. 5–10% is normal.
Everything is calculated in your browser. Nothing you type is sent anywhere or stored.
Bags or bulk delivery?
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Coverage & weight
Material profile
For the calculator’s default 10 x 8 ft footprint with a 1 ft backfill band at 12 inches deep, you’ll need about 1.63 cubic yards, or roughly 2.25 tons of crushed gravel backfill including a 10% waste allowance. That’s around 88 bags if you’re buying by the bag instead of in bulk.
Backfill needed for common trench and foundation sizes
These estimates use crushed gravel backfill at 2,700 lb per cubic yard with a 10% waste allowance built in.
| Project | Depth | Cubic yards | Tons |
|---|---|---|---|
| Utility trench, 20 sq ft footprint | 12 in | 0.81 yd³ | 1.10 tons |
| Longer utility trench run, 60 sq ft footprint | 12 in | 2.44 yd³ | 3.30 tons |
| Foundation wall backfill, 100 sq ft footprint | 18 in | 6.11 yd³ | 8.25 tons |
| Larger foundation backfill, 150 sq ft footprint | 18 in | 9.17 yd³ | 12.38 tons |
| Pipe bedding & cover, 30 sq ft footprint | 6 in | 0.61 yd³ | 0.83 tons |
Backfill material types, weight and drainage
| Type | Weight per yd³ | Best for | Drainage |
|---|---|---|---|
| Native soil (reused excavation spoil) | 2,100 lb | General trench & foundation backfill | Variable |
| Crushed gravel backfill | 2,700 lb | Utility trenches, drainage-friendly fill | Good |
| Sand backfill | 2,600 lb | Pipe bedding & backfill | Excellent |
Figures are for dry material. Wet or freshly delivered material can weigh noticeably more.
How to calculate backfill you need
- Measure the footprint trench length × width, or a foundation’s perimeter × backfill band width, in feet.
- Set the fill depth 12in for a utility trench, 18in for foundation wall backfill, 6in for pipe bedding.
- Convert to cubic yards multiply area by depth in feet to get cubic feet, then divide by 27.
- Add waste add about 10% for compaction settling and spillage while shoveling or wheelbarrowing.
- Convert to tons multiply cubic yards by the material’s density (2,100-2,700 lb/yd³) and divide by 2,000.
Worked example
Using the calculator’s default trench backfill — a 10 ft x 8 ft footprint with a 1 ft backfill band at 12 inches deep, filled with crushed gravel backfill:
- Backfill area10 x 8 ft footprint, 1 ft band = 40 sq ft
- Depth in feet12 in ÷ 12 = 1.0 ft
- Volume40 sq ft × 1.0 ft = 40 cu ft
- Plus 10% waste40 × 1.10 = 44 cu ft
- Cubic yards44 ÷ 27 = 1.63 yd³
- Weight (crushed gravel backfill, 2,700 lb/yd³)1.63 × 2,700 = 4,400 lb
- Tons4,400 ÷ 2,000 = 2.2 tons
- Order amountround up to 2.25 tons, or about 88 bags at 0.5 cu ft each
Recommended depth by project
| Project | Recommended depth | Notes |
|---|---|---|
| Utility trench | 12 in | Standard depth for water, electric, or irrigation line trenches |
| Foundation wall backfill | 18 in | Backfilling against a foundation or retaining wall after forms are stripped |
| Pipe bedding & cover | 6 in | Cushioning and initial cover layer above a pipe before deeper backfill |
| Fence post / footing backfill | 6-12 in | Filling around posts or small footings after setting |
| Deep trench (sewer / main line) | 24-36 in | Backfill in lifts with compaction between each lift |
Bags or bulk delivery?
Bagged backfill (roughly 0.5 cu ft per bag) makes sense for a single fence post hole or a short repair run, but trenches and foundation perimeters add up fast. Once you’re past a ton or so, bulk delivery plus the flat delivery fee is cheaper and much less labor than carrying bags to the trench.
- Small repairsunder 0.5 ton (about 20 bags) — fence posts and short patch runs are easy with bags.
- Medium trenches0.5 to 3 tons — compare total bag cost against bulk price plus delivery before deciding.
- Foundation & long trenchesover 3 tons — bulk delivery is cheaper and far less labor than stacking bags.
Common mistakes
- Reusing unsuitable native soilclay-heavy or rocky spoil compacts poorly and can trap water against a foundation — imported gravel or sand backfills more reliably in those cases.
- Backfilling without compacting in liftsdumping fill in all at once, rather than in 6-8in lifts with compaction between each, leaves voids that settle later and can crack pavement or slabs above.
- Skipping pipe beddingbackfilling directly on an uneven trench bottom lets a pipe rest on point loads instead of even support, risking cracks under later loads.
- Backfilling too soon against a foundation wallgreen concrete or unbraced walls can crack or shift under backfill pressure — wait for adequate cure time and bracing first.
- Ignoring drainage behind retaining structuressolid, poorly draining backfill against a wall builds up hydrostatic pressure — use free-draining gravel and a drain line where water can collect.
- Not accounting for settling over utilitiestrench backfill over pipes and cables settles over the following months — crown it slightly above grade or plan a follow-up top-off.
What this calculator assumes
Adjust your result if your project differs from these.
- Depth is the finished, settled fill depth, not a loosely dumped depth.
- Density varies by material — native soil, gravel, and sand are not interchangeable in weight.
- 10% waste covers compaction settling and spillage during placement.
- Prices are for material only; excavation, compaction equipment, and hauling spoil away are separate.
- The trench or excavation is assumed graded and free of standing water before backfilling.
- Bag coverage assumes 0.5 cu ft bags; bulk delivery is more economical above roughly 1 ton.
Common questions
How much backfill do I need for a trench?
For a 20 sq ft trench footprint at 12 inches deep, you’ll need about 0.81 cubic yards, or roughly 1.1 tons of backfill — enter your own trench dimensions above for an exact figure.
Can I use the dirt I dug out as backfill?
Often yes for general trench fill, but native soil compacts unevenly compared to crushed gravel or sand, and clay-heavy spoil can trap water against foundations and pipes.
What's the best backfill material for a utility trench?
Crushed gravel compacts well and drains freely, making it a common choice for trenches around pipes and cables where drainage matters.
How deep should foundation backfill be?
Typically 18 inches or more, matching the depth of the excavated area around the foundation wall down to undisturbed soil or footing grade.
Do I need to compact backfill in layers?
Yes — compact in 6-8 inch lifts rather than filling all at once, or the material won’t reach even density and will settle unevenly later.
What is pipe bedding and cover?
A thin layer (often 6 inches) of sand or fine gravel placed under and over a pipe before the main backfill, so the pipe rests on even support rather than point loads.
How much does backfill cost?
For the calculator’s default 40 sq ft, 12in-deep example, expect roughly $158 for a bulk load including delivery, or around $440 buying by the bag.
Is sand or gravel better for backfill?
Sand is easiest to compact around pipes and in tight spaces; gravel drains better and resists erosion, making it common for trenches near foundations.
How long after backfilling can I pave over a trench?
Wait until the fill has been compacted in lifts and had time to settle — paving over uncompacted backfill almost always leads to a sunken trench line later.
Does backfill settle over time?
Yes, even well-compacted backfill can settle slightly over the following months as it consolidates under its own weight and moisture cycles — crown it a bit above grade to compensate.
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Project
| Shape | — |
| Dimensions | — |
| Depth | — |
| Area | — |
| Material | — |
| Waste allowance | — |
Volume & weight (incl. waste)
| Cubic yards | — |
| Cubic feet | — |
| Weight | — |
| Tons (rounded up) | — |
Shopping list
| Bulk order | — |
| Bagged alternative (0.5 cu ft) | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes uniform depth and standard dry material densities. Confirm quantities with your supplier before ordering.