Working out volume for any area shape
Every gravel calculation starts the same way: area multiplied by depth. The only thing that changes is how you find the area for the shape you're covering.
Rectangular
V = L × W × D
A 10 × 10 ft path at 2 in deep: 10 × 10 × (2÷12) = 16.7 cu ft ≈ 0.62 cu yd.
Circular
V = π × r² × D
A 10 ft diameter circle (r=5) at 2 in: π × 25 × (2÷12) ≈ 13.1 cu ft.
Triangular
V = ½ × B × H × D
A 10 ft base, 8 ft height bed at 2 in: 0.5 × 10 × 8 × (2÷12) ≈ 6.7 cu ft.
Whichever shape you use, remember to convert depth from inches to feet (divide by 12) before multiplying — it's the single most common place a hand calculation goes wrong.
How deep should the gravel layer be?
| Project | Typical depth |
|---|---|
| Decorative top layer / mulch bed | 2 in |
| Walkway or garden path | 2-3 in |
| Driveway base layer | 4-6 in |
Driveways usually need a base layer for structural support plus a thinner top layer for appearance and drainage — run the calculator once for each layer if your project uses both.
From volume to tons and dollars
Gravel is priced and delivered by weight, not volume, so the next step converts cubic yards into tons using the material's density — around 105 lbs per cubic foot for typical gravel, though the exact figure varies by stone type:
Weight = Volume (cu ft) × Density (lbs/cu ft)
At the default 105 lbs/cu ft, one cubic yard (27 cu ft) weighs 27 × 105 = 2,835 lbs — right around 1.4 tons, which is the rule of thumb most suppliers quote.
Once you know the tonnage, multiplying by your supplier's price per ton or per yard gives the delivery cost — and it's worth ordering 5-10% extra to cover compaction and an uneven subgrade, the same reasoning that applies to concrete and other bulk materials.
Related tools
If your project also involves a mulch bed alongside the gravel, the Mulch Calculator uses the same area-times-depth approach. For a poured concrete section of the same driveway, the Concrete Calculator handles volume and bag counts the same way.