Shed base gravel calculator
Work out the compacted gravel pad a shed, greenhouse or outbuilding sits on.
Shed base gravel calculator
Work out the compacted gravel pad a shed, greenhouse or outbuilding sits on.
Enter your dimensions to see how much gravel you need.
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Results are estimates for planning. Bulk density varies by supplier, moisture and how much the material is compacted, so confirm quantities with your supplier before ordering.
Shed base gravel calculator
What a shed base is actually for
A gravel shed base does two jobs: it spreads the shed's weight over a wider area than the bare footprint so the ground underneath doesn't settle unevenly, and it lifts the floor above grade so water drains away from the structure instead of sitting under it. Skipping it, or building it too shallow, is why a shed that looked level on installation day is visibly tilted a year later.
Sizing it larger than the shed itself
A base built exactly to the shed's footprint tends to erode at the edges, since that's where water sheds off the roof and concentrates. Extending the gravel pad 6 to 12 inches beyond each side of the shed on every edge is common practice, and it's worth adding into the dimensions you enter here rather than calculating the bare footprint and hoping the edges hold.
Depth and material
Four to six inches of a compacting material like crusher run is a typical starting point, more on soft ground. This needs to be a material that locks together under compaction, the same reason a driveway base uses it, not a decorative or rounded stone that will shift under the shed's point loads over time.
Treating the base as a structure, not a surface
A shed base does more work than its appearance suggests, and that is worth keeping in mind before treating this calculator as a simple area times depth exercise. The compacted gravel pad underneath a shed, greenhouse or outbuilding is carrying the full weight of the structure and whatever is stored inside it, it is managing drainage so water moves away from the floor rather than pooling under it, and it is the one layer that is effectively impossible to fix once the building is sitting on top of it. That combination is why the depth and compaction choices here matter more than they would for a purely decorative area of similar size, even though the arithmetic driving the quantity is the same.
Sizing the base larger than the shed's own footprint is a detail that is easy to skip when measuring, since it is tempting to just measure the building kit's dimensions and stop there without adding anything to either side. In practice a base built flush with the shed's edges tends to erode or settle at the perimeter first, exactly where rain runs off the roofline and concentrates after every storm, and a base with no margin leaves no room for the building to be positioned slightly off center without an edge hanging over bare ground. Building the base a modest amount larger than the shed footprint on each side, then entering that larger area into this calculator rather than the building's own dimensions, avoids both problems at once and gives the finished pad a visible margin all the way around the structure. That margin also makes future maintenance easier, since a shed with a gravel apron around it gives you somewhere to stand to paint, repair or re-roof the structure without stepping directly onto bare soil that turns to mud the moment it rains.
Depth and material both follow from what the base has to resist, rather than from a single rule of thumb that applies to every outbuilding. Crusher run is the standard choice here rather than a rounded or decorative stone, because its angular particles lock together under compaction in a way rounded gravel cannot, giving the base the load bearing stability a shed floor needs to stay level under stored weight. If the shed sits in a wet or poorly draining spot, it is worth checking the drainage gravel calculator for how a drainage layer is typically sized separately from the structural base, since the two jobs call for different depths and sometimes different stone even on the same site, depending on how the water actually moves across the ground.
Ground preparation ahead of delivery affects the final result as much as the gravel itself does, and it is a step that is easy to shortcut when the gravel is already on its way. Compacted gravel placed on soft, unprepared soil will settle unevenly as the soil beneath it consolidates over the following seasons, which shows up later as a shed floor that is no longer level even though the gravel layer itself never changed. Removing topsoil and organic material down to firmer ground before gravel goes in, and compacting that subgrade before the first lift of crusher run arrives, is what keeps the base stable for the life of the structure rather than for its first year, when settling has not yet had time to show. Skipping this step is tempting because it adds a day or more of labor before any gravel even arrives, and the difference is invisible on delivery day, but it is the single most common reason a shed floor that started level develops a noticeable tilt within a couple of seasons of use.
If the shed base connects to or borders a slab, a concrete footing, or a wider paved area rather than standing alone in a lawn, the concrete slab gravel calculator and the paver base calculator use closely related base logic and are worth cross-checking so adjoining sections of the site end up with a consistent depth rather than an abrupt step between two different builds poured at different times. Once the base volume is settled, running it through the gravel cost calculator gives a realistic materials budget before any ground gets disturbed.
Frequently asked questions
How deep should a gravel base be for a shed?
Four to six inches of compacted crusher run is a common starting point for a typical garden shed on reasonably firm ground, with more depth on soft or wet ground. This is a general starting point rather than a specification; a large or heavy shed, or genuinely poor ground, may need more, and the manufacturer's own base instructions should take priority if they specify something different.
Should the gravel base be bigger than the shed?
Generally yes, by 6 to 12 inches on each side. Water running off the roof edge lands just past the shed's footprint, and a base that stops exactly at the wall tends to erode right where that runoff concentrates. Enter the padded dimensions, not just the shed's own footprint, into the calculator above.
What size shed base do I need?
The base should be at least as large as the shed's footprint, and extending it 6 to 12 inches beyond each side is common practice. Water running off the roof edge lands just past the shed's footprint, and a base that stops at the wall tends to erode where that runoff concentrates. Enter the padded dimensions, not just the shed's own footprint.
What kind of gravel is best for a shed base?
A material that locks together under compaction, such as crusher run or dense graded crushed stone, is the right choice. Decorative or rounded stone that shifts under load is the wrong material for a shed base, because the shed's point loads will cause uneven settling over time. The calculator defaults to crusher run for that reason.
How do I prepare the ground before laying gravel?
Remove any grass, organic material and loose topsoil from the area. The organic layer decomposes and creates voids under the gravel, leading to uneven settling. Level the exposed soil and compact it before adding the first layer of gravel. The calculator gives you the gravel quantity; ground preparation is the step that makes it last.
Can I build a shed on a gravel pad without concrete?
Yes, a properly built gravel pad is a common and effective alternative to a concrete slab for most garden sheds. The gravel spreads the shed's weight, provides drainage and lifts the floor above grade. The key is proper depth, compaction and a level surface. The calculator gives you the gravel quantity for your shed's dimensions.
How much does a gravel shed base cost?
For a typical 8 by 10 foot shed with a 4 inch base, you need about 1 cubic yard of crusher run, which is roughly 1.5 tons. At typical prices, that is a modest material cost. Enter your own shed dimensions and supplier price above for the exact quantity and cost for your project.
Do I need a perimeter frame for a gravel shed base?
A frame made of pressure treated lumber or landscape timbers helps contain the gravel and keeps the edges from spreading. It also makes it easier to achieve a level surface. Without a frame, the gravel tends to erode at the edges over time. The calculator gives you the gravel quantity; adding a perimeter frame is a practical step that improves durability.