How to Calculate How Much Gravel You Need
The formula is straightforward: multiply your area in square feet by your desired depth in feet, then divide by 27 to convert cubic feet to cubic yards.
cubic yards = (length × width × depth in feet) ÷ 27For a 20 ft × 10 ft driveway section at 3 inches deep: (20 × 10 × 0.25) ÷ 27 = 1.85 cubic yards. Add 10% for compaction: 2.04 cubic yards — round up to 2.1 yards to order.
Worked Example: Standard Driveway Section
- Dimensions: 60 ft long × 12 ft wide
- Gravel base depth: 4 inches (0.333 ft)
- Area: 720 sq ft
- Volume: 720 × 0.333 = 239.8 cu ft = 8.88 cu yd
- With 10% compaction factor: 9.77 cu yd
- Weight at 2,700 lb/yd³: 13.2 tons
Material Density Reference
| Material | lb/yd³ | Tons/yd | Typical Use |
|---|---|---|---|
| Pea Gravel | 2,700 | 1.35 | Decorative, drainage |
| Crushed Stone #57 | 2,700 | 1.35 | Base layer, drainage |
| Crushed Stone #411 | 2,875 | 1.44 | Driveway base |
| Crusher Run (#21A) | 2,850 | 1.43 | Compactable base |
| River Rock | 2,835 | 1.42 | Landscaping, stream beds |
| Decomposed Granite | 2,565 | 1.28 | Paths, patios |
| Lava Rock | 1,215 | 0.61 | Decorative, fire pits |
Source: Braen Stone bulk material data; USGS bulk density tables. Densities assume dry, loose material — wet gravel can weigh 5–10% more.
How Much Depth Do You Need?
| Application | Recommended Depth |
|---|---|
| Decorative landscape bed | 2–3 inches |
| Garden path | 2–3 inches |
| Driveway surface layer | 2–3 inches |
| Driveway base (compacted) | 4–6 inches |
| Parking area base | 6–8 inches |
| French drain backfill | 12+ inches |
| Shed base | 4 inches minimum |
Bags vs. Bulk Delivery
A 0.5 cu ft bag of gravel (about 50 lb) costs $4–$7 at a home center. At bulk rates of $35–$55 per ton delivered, bags cost 3–5× more per cubic yard. For anything over about 1 cubic yard (50 sq ft at 3 in deep), bulk delivery is more economical even with a $50–$100 delivery fee.
Common Mistakes
- Ordering by bags for large areas: 54 half-cubic-foot bags = 1 cubic yard. That is expensive and heavy to handle. Call a local quarry or landscape supplier for bulk pricing.
- Skipping the waste factor: Gravel compacts 10–15% as it settles, especially crusher run. Always order at least 10% extra.
- Mixing up tons and cubic yards: Gravel is sold both ways. Confirm with your supplier which unit their price refers to — 1 cubic yard ≠ 1 ton.
- Underestimating depth: A driveway base at 2 inches instead of 4 will rut and need topping off within a season.
Safety note: Call 811 (the national Dig Safe line) before any excavation, even shallow grading. Underground utilities can be surprisingly close to the surface.