Gravel Base Calculator
Calculate tons of road base for a slab, shed, or paver base layer using its 1.5 tons per cubic yard density, plus total cost.
How this calculator works
A gravel base layer is priced and delivered by the ton, so this calculator converts your area and depth into cubic yards, then multiplies by road base’s compacted density of 1.5 tons per cubic yard to get the tons you need to order.
Formula: Cubic yards = (Length ft × Width ft × Depth ft) ÷ 27. Tons = Cubic yards × 1.5.
Worked example
A 20 ft × 10 ft base area at a 4-inch depth:
- Depth in feet: 4 ÷ 12 = 0.3333 ft
- Cubic yards: (20 × 10 × 0.3333) ÷ 27 ≈ 2.4694 yd³
- Tons: 2.4694 × 1.5 ≈ 3.70 tons
- At $40/ton, that’s $148.15 before waste.
Coverage reference
| Area | Tons needed (at 4 in) |
|---|---|
| 10 ft × 5 ft | 0.93 tons |
| 20 ft × 10 ft | 3.70 tons |
| 40 ft × 20 ft | 14.81 tons |
How to measure your area
Measure the length and width of whatever the base is supporting — a slab, a shed footprint, or a paver patio — in feet, extending a few inches beyond the finished surface’s edge if your project calls for the base to run wider than what’s on top of it. Match the depth to the load the base needs to carry, not a single default number, since a paver walkway and a driveway have very different requirements.
Frequently asked questions
What projects use a generic gravel base layer?
Concrete slabs, shed and outbuilding foundations, paver patios and walkways, and any structure that needs a stable, well-drained layer between the native soil and the finished surface. A compacted gravel base spreads point loads, resists frost heave, and keeps water from pooling under the structure.
How deep should a gravel base be, and does it change by load?
As a rule of thumb: 2-4 inches under light pedestrian pavers, 4 inches under a shed or concrete slab on decent soil, and 6-8 inches or more under a driveway, heavy paver patio, or anywhere vehicles will drive. Soft or clay-heavy native soil generally pushes every one of those numbers up.
Why does this calculator use road base's 1.5 tons per cubic yard density by default?
Road base (also sold as crusher run or Class 5 in some regions) is the most common general-purpose base material because its mix of crushed stone and fines compacts into a dense, stable layer — a better foundation property than clean, fines-free gravel, which stays looser.
Do I need geotextile fabric under a gravel base?
It's recommended on soft, wet, or clay-heavy soil, where fabric keeps the base material from working its way down into the mud over time (and mud from working up into the base). On firm, well-drained native soil, some builders skip it, but it's cheap insurance against long-term settling.
How many lifts should I compact a gravel base in?
Compact in lifts no thicker than 4 inches. A single thick lift often leaves the bottom portion loose because a plate compactor's energy doesn't fully penetrate deep material, leading to uneven settling under the finished surface later.
Should I add waste when ordering a gravel base?
Yes, the 10% waste toggle accounts for compaction settling and an uneven excavated subgrade, both common regardless of what's being built on top of the base.
Estimates only. Verify quantities with your supplier before purchasing.