Add 2 feet to each shed dimension so the pad extends 12 inches past every wall, multiply by 5 inches of depth in feet, divide by 27, then multiply by 1.55 for tons of crusher run. A 10 × 12 ft shed needs a 12 × 14 ft pad — about 2.6 cubic yards, or 4 tons.
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Shed Base Calculator Guide
A shed lives or dies by what is under it. Set on bare ground, even a quality building racks out of square as the soil heaves and settles, and the door is always the first thing to stop closing. A compacted gravel pad solves all of it at once: level bearing, drainage under the floor, and a capillary break that keeps ground moisture out of the framing.
The one rule that surprises first-time builders: the pad is bigger than the shed. Extend it 12 inches past every wall — add 2 feet to each shed dimension and enter that pad size, and the calculator converts it at a 5-inch depth of crusher run, 1.55 tons per cubic yard.
What Size Gravel Pad Does Your Shed Need?
| Shed | Pad size | Cubic yards at 5 in | Tons (crusher run) |
|---|---|---|---|
| 8 × 8 ft | 10 × 10 ft | 1.5 | 2.4 |
| 10 × 12 ft | 12 × 14 ft | 2.6 | 4.0 |
| 12 × 16 ft | 14 × 18 ft | 3.9 | 6.0 |
| 12 × 24 ft | 14 × 26 ft | 5.6 | 8.7 |
That 12-inch apron is not cosmetic. It catches roof drip-line water before it undercuts the pad edge, keeps rain splash off the siding, and guarantees the skids sit on full bearing even if the shed lands a few inches off the mark on delivery day.
Building the Pad: Level First, Compact Always
- Excavate sod and topsoil 4–6 inches down across the full pad footprint — organics under a pad rot and sink.
- Square a frame of 4×6 timbers or steel edging if the site slopes, setting the frame dead level with a 4-ft level on a straightedge.
- Lay fabric over the subgrade so the stone cannot migrate into the soil.
- Fill in two lifts, compacting each with a plate compactor; a single 5-inch loose lift never densifies at the bottom.
- Screed the surface flat against the frame or a string grid. The flatter the stone, the less shimming the shed needs.
Check the pad with a level one last time before the building arrives — corrections cost minutes now and a jack-and-shim afternoon later. For a closer look at why crusher run is the pad material of choice, see the crusher run calculator; if your shed will sit on pavers instead of skids, the paver base calculator handles that variant.
Frequently Asked Questions
How much bigger than the shed should the gravel pad be?
Extend the pad 12 inches beyond the shed footprint on all four sides — so a 10 × 12 ft shed sits on a 12 × 14 ft pad. The border catches roof drip, keeps splash off the siding, and gives the runners full bearing even if placement is slightly off.
How deep should a shed gravel base be?
Four to six inches of compacted stone is the standard, with 5 inches a solid middle ground for garden sheds. Go to 6 inches on soft ground or under heavy workshops, and always compact in two lifts rather than one.
What gravel is best under a shed?
Crusher run compacts into the firmest, most stable pad and is the usual choice at 1.55 tons per cubic yard. Some builders top it with an inch of washed #57 for drainage; avoid pads of #57 alone, since the shed can slowly shift on stone that never locks.
Do I need a timber frame around a shed pad?
On level ground a well-compacted pad holds its edges without one, but a 4×6 timber or steel edging frame keeps the perimeter crisp and is close to essential on any slope. Set the frame level first and screed the stone flush to its top.