How much does drainage rock cost?
Enter the drainage area, rock depth, supplier density, and price per ton. The calculator estimates material cost only; pipe, fabric, basins, excavation, grading, delivery, and labor are separate.
Pipe and fabric are not included
This calculator estimates rock volume only. Pipe diameter, fabric wrap, trench shape, catch basins, cleanouts, outlets, and surface grading should be planned separately.
Use drainage-suitable rock
Decorative stone is not always the right material for drainage. Confirm aggregate size and drainage suitability with the supplier or project specification.
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 culvert end rock cost: 274 USD
How to estimate culvert end rock 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 drainage rock cost?
Calculate drainage rock volume from area and depth, convert it to tons using supplier density, then multiply by price per ton and add waste.
Does this subtract pipe volume?
No. It estimates the trench rock volume as a planning number. Pipe, fabric, and void space can change real usage.
What depth should I use?
Use the rock depth planned for the trench, not the total landscape surface depth. Check the project specification before ordering.
Can I use decorative rock for a French drain?
Do not assume so. Use a drainage-suitable aggregate recommended for the project.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.