Shed Base Gravel Calculator
Use this shed base gravel calculator to size a shed foundation gravel base in tons and cubic yards. Pick your shed, and it adds the border the pad needs past the walls, adjusts weight for the gravel grade, and tells you if the stone you picked will actually hold.
Your result
What to order
4.5 tons of #57 crushed stone for a 12 by 14 ft pad, 6" deep
Gravel is sold in half-ton steps once you are past a ton.
- Pad footprint
- 168 sq ft, against 120 sq ft of shed. The extra is the 1 ft border on all four sides.
- Excavate to
- 6" below finished level, so the top of the gravel sits flush with the ground rather than proud of it.
- How this is worked out
- 12 × 14 ft = 168 sq ft × 6" ÷ 12 ÷ 27 = 3.11 yd³ × 2,800 lb ÷ 2,000 = 4.36 tons
Calculate gravel for your shed base
Pad width × pad length × depth ÷ 27 gives cubic yards, then multiply by 1.4 for tons of #57 stone. A 10 by 12 shed needs about 4.4 tons.
- Add a foot to every side. A 10 by 12 shed sits on a 12 by 14 pad. This is the step people skip, and it is why so many pads wash out at the edges.
- Pick a depth. Six inches suits most sheds. Four is enough for something light on firm ground, 8 for a workshop or wet clay.
- Choose the grade before the quantity. Density runs from 2,700 to 3,000 lb a yard depending on what you order, which moves the tonnage by around 10%.
- Order in tons. Gravel yards quote and weigh by the ton even though they talk in yards.
Gravel for shed base work is one of the few jobs where getting the material right matters more than getting the volume right. An extra half ton costs a few dollars. The wrong stone costs you the pad.
What size gravel for a shed base
Three-quarter inch angular crushed stone, sold as #57. It is the default for a reason: the pieces are big enough to lock against each other and irregular enough that they stay locked.
What size gravel for shed base work comes down to one property, and it is not size at all. It is shape. Angular stone has flat faces that jam together under load and stop moving. Rounded stone does not, whatever size it is.
| Grade | Per cubic yard | Holds a shed? | Notes |
|---|---|---|---|
| #57 crushed stone | 2,800 lb | Yes | The default for shed pads. Angular 3/4" stone that locks together and drains |
| Crusher run (QP) | 3,000 lb | Yes | Stone plus fines, so it compacts hardest. Best under heavy sheds, drains slower |
| #8 crushed stone | 2,750 lb | Yes | Smaller angular stone, 3/8". Fine for light sheds and easier to rake level |
| Pea gravel | 2,700 lb | No | Rounded stone. It will not lock together, so the pad shifts and the shed racks |
Why pea gravel fails
Pea gravel is the one to avoid, and it's the one most people reach for because it is cheap and looks tidy. The stones are rounded river pebbles. Put a shed on them and they behave like ball bearings: the pad spreads sideways under the point loads at the corners, one side drops, and the door stops shutting.
If you already have pea gravel down, you don't have to throw it away. Cap it with 4 inches of #57 and compact that, and the angular layer will do the structural work.
How thick should a gravel shed pad be
Six inches for a standard timber shed. Four is enough for a light plastic one on firm ground, and 8 inches is worth it for a workshop or anywhere the ground holds water.
Depth does two jobs. It spreads the load, so the shed presses on a wide area of soil instead of four small ones, and it gives water somewhere to go before it reaches the underside of the floor. On clay both matter more, which is why the answer creeps up rather than down on heavy soil.
Compact in layers rather than all at once. Two 3-inch lifts with a plate compactor between them gives a far firmer pad than 6 inches dumped and rolled once, and a compactor is a cheap day hire.
How far the pad should extend past the shed
A foot on every side, so a 10 by 12 shed wants a 12 by 14 pad. That border isn't cosmetic.
Rain runs off the roof and lands in a line just outside the walls. If that strip is bare soil it erodes, and once it has washed out a channel the edge of the gravel has nothing holding it in and starts migrating. A foot of stone catches the runoff and lets it soak away instead.
The border also gives you room to stand while you assemble the shed and to walk around it afterwards, which matters more than it sounds when you are trying to paint a wall or clear a gutter.
Edging and containment
Timber edging, steel edging or a course of blocks around the perimeter keeps the pad where you built it. Without containment the edges slump outward over a few seasons and the pad thins at exactly the point carrying the shed corners.
Common shed sizes, and the gravel each one takes
A 10 by 12 shed on a 6-inch pad takes about 3.1 cubic yards, or 4.4 tons of #57 stone. The four sizes below cover most of what people buy.
| Shed | Pad | Cubic yards | Tons of #57 |
|---|---|---|---|
| 8 × 10 ft | 10 × 12 ft | 2.22 | 3.1 |
| 10 × 12 ft | 12 × 14 ft | 3.11 | 4.4 |
| 12 × 16 ft | 14 × 18 ft | 4.67 | 6.5 |
| 12 × 20 ft | 14 × 22 ft | 5.7 | 8 |
Those figures already include the border, which is why the pad column is bigger than the shed column. Going from 4 inches to 8 doubles every tonnage in the table, so depth is the lever that moves cost, not shed size.
Notice how little the tonnage climbs between an 8 by 10 and a 10 by 12. Adding two feet each way costs you about a ton, which at typical rates is under fifty dollars. If you're undecided between two shed sizes, the pad is rarely the reason to go smaller.
If your shed isn't on the list, work the pad out first by adding two feet to each dimension, then multiply width by length by depth in feet and divide by 27. The calculator above does it for any size, including metric.
Gravel vs concrete vs blocks: which base for which shed
Gravel for almost every garden shed. Concrete when the building is large, heavy or permanent. Blocks or piers only where the ground slopes enough that levelling it would mean serious excavation.
Gravel wins on cost, drainage and effort. It needs no formwork, no cure time and no mixer, it can be leveled with a rake and a spirit level, and water runs straight through instead of pooling against the floor. A pad that costs a couple of hundred dollars in stone would be four figures in concrete.
Concrete earns its money for workshops with machinery, anything you plan to drive into, or a building meant to outlast the fence. Blocks suit sloping ground, but they put the load on a few small points, so the shed floor has to be strong enough to span between them.
Shed base cost, and where the money goes
Expect $150 to $400 in stone for a typical shed pad. A 10 by 12 needs about 4.3 tons, and #57 runs roughly $35 to $70 a ton delivered depending on how far you are from the quarry.
Delivery is usually the biggest single line. Gravel is heavy and cheap, so haulage often costs as much as the stone, and yards charge a flat fee inside a radius. Ordering the whole pad in one load rather than two trips is the easiest saving available.
Budget for the extras as well: geotextile fabric to keep the stone out of the soil, edging to hold the pad together, and a day of plate compactor hire. None are expensive on their own, and skipping any of the three is what turns a good pad into one you rebuild in five years. Best gravel for shed base work is whichever angular grade your local yard stocks cheapest.
Shed base gravel FAQ
What kind of gravel for shed base?
Angular crushed stone, not rounded pebbles. #57 crushed stone is the usual choice because the pieces lock together and water drains straight through. Crusher run works too and compacts harder, though it holds water longer because of the fines in it.
What size gravel for shed base?
Three-quarter inch is the sweet spot, which is what #57 stone gives you. Smaller #8 at three-eighths is easier to rake level and fine under a light shed. Anything above an inch leaves voids that are awkward to compact flat.
Can you put a shed on pea gravel?
You can, but it won’t stay level. Pea gravel is rounded, so the stones roll past each other instead of interlocking. Under the point loads of a shed the pad spreads, corners drop, and doors stop closing square. Use angular crushed stone instead.
How much gravel for shed base?
A 10 by 12 ft shed on a 12 by 14 ft pad at 6 inches deep takes about 3.1 cubic yards, or 4.4 tons of #57 stone. Scale from there: every extra inch of depth on that pad adds roughly half a yard.
How thick should a gravel shed pad be?
Four inches for a light plastic or small timber shed on firm ground, 6 inches as the standard, and 8 for a large workshop or soft wet ground. Depth buys you drainage and load spreading, so err deeper on clay.
How far should the gravel pad extend past the shed?
A foot on every side. Rain runs off the roof and lands just outside the walls, and if that strip is bare soil it washes out and undercuts the pad edge. The border also gives you somewhere to stand while building.
Do I need landscape fabric under a shed base?
Yes, a permeable geotextile under the gravel. It stops the stone working down into the soil over the years, which is what makes a pad sink unevenly. Never use plastic sheet, which traps water under the shed.
Is gravel or concrete better for a shed base?
Gravel for most sheds. It drains, costs a fraction of concrete, needs no cure time, and can be leveled by hand. Concrete earns its price for large workshops, anything with heavy machinery, or where you want a permanent floor.