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Gravel is bought by two different units depending on the supplier, cubic yards or tons, and the two only agree once you know the density of the specific material being delivered. This calculator starts from length, width and depth to get a volume, then applies the loose bulk density of whichever material you select, gravel, crushed stone, pea gravel or sand, to convert that volume into a weight. The depth input matters more than it looks: because it is entered in inches and multiplied through the same formula as length and width in feet, a 4 inch pad and a 4 foot pad are 12 times apart in volume, not a rounding difference, so it is worth double checking that field before trusting the output. Delivered depth also settles under compaction, sometimes meaningfully, so a pad ordered at the exact calculated volume can come up slightly short once it is tamped down.

Density is the part of the formula that trips people up, because a single "tons per yard" figure does not exist across materials. Crushed stone runs heavier at roughly 1.6 tons per loose cubic yard, plain gravel around 1.4, pea gravel near 1.5, and sand lighter still at about 1.35, so the same volume of two different materials can differ in delivered weight by more than 15 percent. Sand's lower density also means a sand base requires compaction in thinner lifts than crushed stone to avoid soft spots. That spread is exactly why this calculator asks for a material type rather than returning one generic tonnage figure, and why comparing supplier quotes properly means converting everyone's number to the same unit before deciding who is cheaper.

A gravel base under a fence post or along a fence line is typically a modest 3 to 4 inches, there mainly for drainage rather than structural support, which keeps the volume and tonnage low compared to a driveway or parking pad job using the same calculator. Posts set in gravel instead of concrete rely on free-draining, sandy or rocky soil to hold properly, which is the tradeoff: less rigid than a concrete collar, but better drainage in ground where standing water around the base would otherwise be the bigger problem. Compaction in lifts rather than one pour helps the finished depth stay closer to the ordered volume on larger pads. The post spacing guide and the fence materials guide both touch on when a gravel-only footing is the right call versus when concrete is worth the extra step.

Gravel and concrete are usually compared directly for the same hole, and the fence post concrete calculator runs that comparison from the concrete side using the identical hole dimensions this tool accepts. The embedment depth both approaches need in the first place comes from the fence post depth calculator, and the full reasoning behind choosing one fill material over the other is laid out in the post depth and setting guide. For a bag-based order instead of a tonnage order, the concrete bags calculator covers the same volume logic in bags rather than tons, and if the project also includes a block retaining wall, the retaining wall calculator handles the drainage stone behind it using this same material density approach. The post count driving how many footings need gravel in the first place comes from the fence post calculator, and the rest of the foundation tools sit under the foundation calculators category.

Delivery logistics are worth factoring in alongside the volume and tonnage numbers this calculator produces, since gravel is heavy enough that access matters as much as quantity. A dump truck delivery to a driveway is straightforward, but gravel destined for a backyard fence line or a retaining wall drainage trench often has to be moved by wheelbarrow from a drop point at the curb or driveway, which is worth planning for separately from the tonnage figure itself. Smaller orders, especially for a short run of post holes, are sometimes more practical bought in bags from a home improvement store rather than through a bulk supplier, even though the price per ton is higher that way, simply because a bulk delivery minimum can exceed what a small fence project actually needs. Material choice interacts with purpose as much as with density: crushed stone with angular faces locks together better under compaction than smooth, rounded pea gravel, which is one reason crushed stone is the more common choice under a structural base like a retaining wall footing, while pea gravel or washed gravel is more often chosen for drainage layers or decorative surface applications where interlock matters less than drainage and appearance. None of these choices change the volume-to-weight formula this calculator applies, but they do change which material row in the selector is the right one to pick for a given part of the project.