How to Calculate Pea Gravel
Pea gravel is small rounded stone screened to a 3/8 to 3/4 inch (10 - 20 mm) range. Because the stones are smooth and roughly pea-sized, the material is comfortable underfoot, drains instantly, and looks clean in any landscaping style. It is the most common stone for residential walkways, patios, playground cushioning, pipe bedding, and drainage around foundations. Unlike crushed stone, pea gravel does not compact under load - calculating the right volume and installing a proper base determines whether the surface stays put or scatters within a season.
Volume Formula
Start by multiplying length, width, and depth to find the cubic volume. In imperial units, depth is entered in inches, so divide by 12 to keep all values in feet. In metric units, keep everything in meters:
Convert cubic feet to cubic yards (the standard bulk unit) by dividing by 27, since there are 27 cubic feet in a cubic yard:
Tons and Weight Conversion
Pea gravel weighs roughly 96 pounds per cubic foot (1540 kg per cubic meter). Suppliers sell pea gravel by the ton in the US and by the tonne in metric countries. Convert from cubic feet to tons by multiplying density and dividing by 2000:
One cubic yard of pea gravel weighs about 2,600 pounds (1.3 tons or 1,180 kg). One cubic meter weighs about 1.54 tonnes.
Depth by Application
The correct depth depends entirely on how the pea gravel will be used. Too shallow and the base shows through. Too deep and the stone scatters under any pressure.
| Application | Pea Gravel Depth | Base Layer | Edge Containment |
|---|---|---|---|
| Walkway | 2" (5 cm) | 4" crusher run | Required |
| Patio | 2" (5 cm) | 4" crushed stone | Required |
| Driveway (top) | 2-3" (5-8 cm) | 4-6" crusher run | Critical |
| Playground | 6-12" (15-30 cm) | Compacted sub-grade | Required |
| Pipe Bedding | 6" (15 cm) | Wrap in fabric | Not needed |
| Decorative Bed | 3" (8 cm) | Landscape fabric | Optional |
Coverage Quick Reference
These coverage figures assume pea gravel at 96 lb/cu ft density. Actual coverage varies by 5-10 percent depending on stone moisture content and packing pattern.
| Quantity | Coverage at 2" | Coverage at 3" | Coverage at 6" |
|---|---|---|---|
| 1 ton | ~125 sq ft | ~83 sq ft | ~42 sq ft |
| 1 cubic yard | ~162 sq ft | ~108 sq ft | ~54 sq ft |
| 0.5 cu ft bag | ~3 sq ft | ~2 sq ft | ~1 sq ft |
| 1 m3 (bulk) | ~20 sq m (at 5 cm) | ~13 sq m (at 8 cm) | ~7 sq m (at 15 cm) |
Why Pea Gravel Needs a Base Layer
Pea gravel alone is inherently unstable because its rounded shape does not lock together under load. Every traffic-bearing surface requires a compacted base of angular crushed stone (crusher run, #57 stone, or similar) beneath the pea gravel layer. The angular stones in the base interlock and compact to carry weight, while the pea gravel on top stays loose and comfortable. Without a base, your pea gravel migrates into the soil and effectively disappears within one or two seasons.
- Walkways and patios - compact 4 inches of crusher run to 95 percent Proctor density before placing gravel
- Driveways - compact 4-6 inches of crushed base, finish with 2-3 inches of pea gravel on top
- Playgrounds - 6 inches of pea gravel over undisturbed soil (no base needed)
- Garden beds - only landscape fabric is required, no structural base
Playground Safety Depths
The Consumer Product Safety Commission (CPSC) publishes minimum depth guidelines for pea gravel under play equipment based on fall height:
| Fall Height | Minimum Depth | Typical Equipment |
|---|---|---|
| 5 ft | 6" (15 cm) | Toddler swings, short slides |
| 7 ft | 9" (23 cm) | Standard swing sets |
| 10 ft | 12" (30 cm) | Tall slides, monkey bars |
Bulk vs. Bagged Pricing
Bagged pea gravel at big-box stores costs 4 to 6 dollars per 0.5 cubic foot bag. That works out to 160 to 240 dollars per ton - three to five times the cost of bulk. Bulk delivery from a quarry or landscape supplier runs 35 to 60 dollars per ton plus a delivery fee of 50 to 150 dollars depending on distance and minimum order.
| Project Size | Recommended Purchase | Typical Cost |
|---|---|---|
| Under 0.5 ton | Bagged (big-box) | $80 - $120 |
| 0.5 - 3 tons | Bulk delivery | $150 - $350 |
| 3+ tons | Bulk, multi-ton delivery | $200 - $500 |
Installation Timeline
- Day 1 morning - excavate area to total depth (base + finish)
- Day 1 morning - level and compact subgrade with plate compactor
- Day 1 - install edging, set stakes, verify grade
- Day 1 - spread landscape fabric, overlap seams 6 inches
- Day 1 afternoon - place and compact base layer in 2-inch lifts
- Day 2 - spread pea gravel evenly, rake to grade
- Year 1 - expect to top up 10-15 percent after settling