Free Gravel Calculator – Volume & Weight in Tonnes

How the Gravel Calculator Converts Area and Depth into Tonnes

Aggregate is measured in volume but sold by weight, and that mismatch is the whole reason this calculator exists. You enter the length and width of the area, the depth of the layer you want, and the material — gravel, dry sand, crushed stone, or topsoil — and it returns the volume in cubic metres and cubic feet plus the weight in tonnes and kilograms. Anyone laying a driveway, a garden path, a drainage bed behind a retaining wall, or a soil layer for raised beds needs the tonnage figure, because that is what a supplier quotes and what the tipper truck delivers. Working it out first also lets you check a landscaper's quote instead of taking the number on trust. Two steps. Volume = length × width × depth, with depth entered in inches and divided by 12 to match the feet used for length and width, since coverage layers are shallow relative to the area. Cubic feet then convert to cubic metres by multiplying by 0.0283168. Weight = volume in cubic metres × the material's bulk density. The constants used are 1680 kg per cubic metre for gravel, 1600 for dry sand and for crushed stone, and 1300 for topsoil. Tonnes are simply kilograms ÷ 1000. Bulk density is the weight of loose material including the air gaps between particles, which is why it sits well below the density of the solid rock itself. Here is a driveway. An area 30 feet by 10 feet at 4 inches deep gives 30 × 10 × (4 ÷ 12) = 100 cubic feet, which is 2.83 cubic metres. Multiply by 1680 kg per cubic metre and you get 4,757 kg, or 4.76 tonnes of gravel. Now see what depth does: keep the same area but go to 6 inches and the volume rises to 150 cubic feet, 4.25 cubic metres, and 7.14 tonnes. Two extra inches added nearly two and a half tonnes to the order, which at typical delivered rates is a meaningful jump in cost. The jobs where this matters are ordinary ones. A homeowner edging a 20 by 3 foot garden path with decorative gravel at 2 inches needs only 0.48 tonnes, which is a half-tonne bulk bag rather than a truck delivery. Someone filling raised beds measuring 12 by 8 feet with 3 inches of topsoil needs 0.88 tonnes, and because topsoil is lighter at 1300 kg per cubic metre, the same volume of gravel would have weighed a third more. A contractor building a French drain calculates the crushed-stone backfill by trench dimensions rather than surface area. And anyone comparing two supplier quotes needs both on the same basis, since one may price per tonne and the other per bulk bag of a stated weight. Depth is what beginners get wrong, in both directions. Skimping on a driveway at 2 inches leaves gravel that rutts and scatters under car tyres within a season; a decorative border at 6 inches is simply money buried in the ground. Gravel also compacts and settles, so a layer laid at 4 inches loose finishes closer to 3 inches, and it is worth ordering for the loose depth. Treat the weight as a close estimate rather than an exact figure: wet material can be 10 per cent heavier than the dry density used here, and how tightly a supplier's stock is compacted changes the number too. Round up when ordering, because coming up short means a second delivery charge for a fraction of a load. Everything runs in your browser, so your measurements and material choice are never uploaded or stored.

Gravel Calculator Formula & Method

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