How much gravel do I need?
Measure the coverage area in square feet, enter depth in inches, and convert the volume to cubic yards. A 300 sq ft area at 3 inches deep is about 2.78 cubic yards before waste.
Cubic yards vs tons
The calculator can estimate volume in cubic yards, but many suppliers sell gravel or rock by the ton. Use supplier density to convert between volume and weight when ordering.
Depth, compaction, and waste
Decorative rock, paths, driveways, and base layers use different depths. Compacted base material may need more loose material than the finished compacted depth suggests.
What affects gravel cost?
Material type, haul distance, delivery minimums, density, compaction, and base prep all affect final cost. The calculator focuses on material math, not a contractor quote.
French drain rock example estimates
Examples treat trench length x trench width as area. Pipe, fabric, trench shape, and void space are not subtracted.
| Trench example | Length x width x rock depth | Cubic yards |
|---|---|---|
| Short drain run | 30 ft x 1 ft x 12 in | 1.11 cu yd |
| Medium drain run | 50 ft x 1 ft x 18 in | 2.78 cu yd |
| Wide trench | 50 ft x 1.5 ft x 18 in | 4.17 cu yd |
| Long drain run | 100 ft x 1 ft x 18 in | 5.56 cu yd |
Drain rock coverage by depth
Coverage assumes 1 cubic yard, which is 27 cubic feet. Waste, compaction, settling, and irregular grade are not included.
| Depth | Coverage from 1 cu yd | Coverage from 2 cu yd |
|---|---|---|
| 1 in | 324 sq ft | 648 sq ft |
| 2 in | 162 sq ft | 324 sq ft |
| 3 in | 108 sq ft | 216 sq ft |
| 4 in | 81 sq ft | 162 sq ft |
| 6 in | 54 sq ft | 108 sq ft |
| 12 in | 27 sq ft | 54 sq ft |
Common density planning values
Use supplier-provided density for final tonnage. These broad values are planning placeholders, not product specifications.
| Material | Broad planning density | Notes |
|---|---|---|
| Gravel / crushed stone | 2,600-3,000 lb/cu yd | Varies by gradation, moisture, and compaction. |
| Sand | 2,400-3,000 lb/cu yd | Moisture can noticeably change weight. |
| Topsoil / dirt | 1,800-2,600 lb/cu yd | Moisture and organic matter change density. |
| Mulch | 400-1,000 lb/cu yd | Usually ordered by volume, not weight. |
| Compost | 800-1,500 lb/cu yd | Depends on moisture and material mix. |
Before you calculate
- Measure drain length, width, and rock depth separately from decorative landscape areas.
- Keep pipe, fabric, basin, outlet, and cover-depth details visible as separate planning items.
- Calculate separate drain runs when width, depth, pipe detail, or aggregate type changes.
Common mistakes
- Treating a drainage trench like a shallow decorative rock bed.
- Ordering decorative rock without confirming drainage-suitable aggregate.
- Forgetting that trench shape, pipe, fabric, and uneven bottoms can change real usage.
Formula
cost = ((area * (depth / 12) / 27) * (1 + wastePercent / 100) * densityPerCubicYard / 2000) * pricePerTon
Assumptions
- Depth is entered in inches.
- Density and price per ton vary by quarry, moisture, gradation, and compaction.
- Delivery, base prep, fabric, grading, disposal, and labor are separate.
Example
Estimated trench drain gravel cost: 207 USD
How to estimate trench drain gravel cost
- Measure project area and planned depth, then estimate material volume.
- Enter supplier density so the calculator can convert volume into tons.
- Enter price per ton and include waste or delivery buffer if applicable.
- Multiply estimated tons by the price per ton to get a planning cost.
- Confirm local price, delivery minimums, moisture, compaction, and tax or fees with the supplier.
Before you buy materials
- Confirm aggregate size and drainage suitability with the supplier or project specification.
- Round up for trench irregularity, placement loss, and delivery units.
FAQ
How do I estimate trench drain gravel cost?
Estimate trench drain gravel cost by using the measured quantity as a cost input, then multiplying by material price, labor or unit price, delivery, and waste where relevant. The default example returns 207 USD. Quantity detail: Use cubic yards = area x (depth inches / 12) / 27, then add waste if needed. For a cost estimate, use that quantity as the buying amount, then multiply by unit price and add labor, delivery, prep, waste, and local charges where relevant.
How many square feet does 1 cubic yard of gravel cover?
One cubic yard covers about 162 sq ft at 2 inches deep, 108 sq ft at 3 inches, 81 sq ft at 4 inches, or 54 sq ft at 6 inches before waste. For a cost estimate, use that quantity as the buying amount, then multiply by unit price and add labor, delivery, prep, waste, and local charges where relevant.
Should I order gravel by yards or tons?
Use the unit your supplier sells. Cubic yards estimate volume, while tons estimate weight. Density connects the two. For a cost estimate, use that quantity as the buying amount, then multiply by unit price and add labor, delivery, prep, waste, and local charges where relevant.
Should I include compaction?
Yes for base layers and driveways. Compaction, subgrade variation, and delivery loss are common reasons to include waste.
Does this replace a site estimate?
No. It is a planning calculator. Final quantity depends on grade, base condition, material type, and supplier delivery units.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.