Set dimensions, depth, density, and compaction to match site conditions today easily. Get quantities in multiple units, plus clear costs for ordering right now.
These examples show typical drainage layer estimates. Adjust to your site and supplier.
| Scenario | Shape | Dimensions | Depth | Waste | Required volume | Approx. weight | Sample cost |
|---|---|---|---|---|---|---|---|
| French drain | Trench | 25 ft × 12 in | 12 in | 10% | ~1.37 yd³ | ~1.54 short tons | @ $45/yd³ → ~$62 |
| Planter drainage | Rectangular | 10 ft × 4 ft | 4 in | 7% | ~0.55 yd³ | ~0.62 short tons | @ $38/ton → ~$24 |
| Tree ring | Circular | 6 ft diameter | 3 in | 8% | ~0.33 yd³ | ~0.37 short tons | @ $6.99/bag (0.5 ft³) → ~$126 |
Drain rock is a coarse aggregate layer that creates reliable pathways for water to move away from roots, hardscapes, and foundations. In garden work it is commonly used beneath french drains, behind retaining walls, under raised beds, and around downspout outlets. The goal is predictable flow without clogging. Good drainage also reduces frost heave beneath paths and patios.
For drainage, clean, angular stone in the 3/4 in to 1.5 in range is widely used because it locks together yet leaves voids for water. Rounded river rock drains well but can shift under load. Avoid “fines” unless your design includes fabric separation to prevent migration.
Light garden drainage layers often run 3–6 inches deep under planters and small channels. French drains frequently use 10–18 inches of rock depending on pipe diameter and trench width. Behind retaining walls, 12 inches is a common starting point, increasing with wall height and soil type.
Material loss happens through spillage, uneven trench bottoms, and over-excavation. A waste allowance of 5–12% is practical for most DIY jobs, while complex runs with multiple tie-ins can justify higher. The calculator applies waste to your geometric volume before converting units.
Unlike soil, rock does not “compact” dramatically, but placement, raking, and vibration can reduce voids and settle the layer. Contractors often plan a factor around 1.05–1.15 to cover bulking, moisture variation, and how tightly the rock packs in the trench.
Bulk density varies by quarry and moisture. Typical drain rock can be near 90–110 lb/ft³. Weight matters for vehicle capacity, driveway load limits, and hand handling. By entering a ticket density, you can estimate kilograms, metric tons, and US short tons more accurately.
Suppliers may quote by cubic yard, cubic meter, ton, or bag. Volume pricing is convenient for loose delivery, while ton pricing is common when scales are used. Bags are expensive but useful for small projects. The calculator computes totals for each method so you can compare.
Confirm trench dimensions after excavation, verify whether fabric is required, and keep rock clean during storage. If mixing sizes, order consistent gradation for predictable drainage. Always check local disposal rules for excavated soil and plan safe access for delivery trucks or wheelbarrows.
Use a typical drain rock bulk density between 90 and 110 lb/ft³. If your supplier lists kg/m³, enter that instead. When in doubt, use the midpoint and add a little waste for safety.
Choose the unit your supplier bills. Yards are common for dump delivery; tons are common when material is weighed. If you have both quotes, compare totals in the results section.
For straight trenches and simple beds, 5–10% is usually enough. Use 10–15% when excavation is irregular, access is tight, or you expect extra shaping and leveling.
Rock settles modestly after placement and vibration. A factor of 1.05–1.15 covers typical settling and packing differences. Use the lower end for carefully placed layers and the higher end for rough backfill.
Yes. Use the Trench shape and enter trench width and rock depth around the pipe zone. If your trench includes soil backfill above the rock, only include the rock portion in the depth.
Enter your bag size, commonly 0.5 ft³ or 1 ft³. The calculator divides required volume by bag volume and rounds up, helping you avoid running short during installation.
Volume comes from geometry, so size does not change quantity directly. Size affects void space and drainage performance, which can influence the factor you choose and whether you add fabric or filter layers.
Plan drainage layers accurately and keep your budget controlled.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.