Gravel Calculator

The awkward part of ordering gravel is that the space is a volume and the invoice is a weight. Both steps are simple; the conversion between them is where the guessing lives. Start with volume: cubic feet = area (sq ft) × depth (in) ÷ 12, then divide by 27 for cubic yards, because a cubic yard is a cube 3 ft on a side and 3 × 3 × 3 = 27. A 200 sq ft area at 3 inches is 200 × 0.25 = 50 cubic feet, or about 1.85 cubic yards. Now the weight. This calculator uses roughly 1.4 tons per cubic yard, a reasonable planning figure for dry gravel, which puts that area at about 2.6 tons. The US ton here is the short ton of 2,000 pounds, which is what American aggregate suppliers quote. But density is a property of the specific material, and the honest answer is that it varies. Stone type, particle size, how angular the pieces are, how much fine material is mixed in, and how wet the pile is all move the number, and wet material can be meaningfully heavier than the same stone dry. Every supplier knows the density of what is in their yard. Ask them for the conversion for the exact product before placing a large order, and treat this figure as a way to size the job rather than a quote.

Gravel is one of the few materials where the overage is not about cuts or breakage. It is about the material physically taking up less room after it has been placed than it did in the truck. When aggregate is dumped, the pieces sit loosely with air between them. Spreading, raking, watering, plate-compacting and simply driving on it settles them into each other. The finished, compacted depth is therefore less than the loose depth you spread, sometimes noticeably so, and the effect is strongest with crushed material containing fines, which are the particles that migrate into the voids and lock the layer together. The practical consequence is that a driveway ordered as exactly its finished volume comes up thin, and the shortfall shows first as ruts. Suppliers deal with this every day, so tell yours the finished depth and area you want and ask what they would deliver, rather than handing them a bare cubic yardage. There is a second reason to round up: gravel spreads to fill whatever is under it. An excavation is never a flat-bottomed box, soft spots swallow material, and edges creep outward. The cost of a little extra is a pile in the corner of the yard. The cost of running short is a second delivery fee for a fraction of a load.

"Gravel" covers materials that behave very differently once they are on the ground. Crushed stone is quarried rock broken into angular pieces. The sharp faces interlock, so it stays where you put it and compacts into a firm layer. It is the right choice for anything driven on. Rounded gravel — river rock, and the smooth material sold as pea gravel — does the opposite. The rounded pieces roll past one another, so it never really locks up. It migrates out of beds, tracks into the house on shoes, and pushes aside under a tire. It is comfortable underfoot and looks good in a bed; it is a poor driving surface without edging to contain it. Crushed products also come with or without fines, the stone dust left from crushing. Material with fines packs down hard and sheds water, which is what you want in a base course. Material washed clean of fines drains freely and stays loose, which is what you want in a French drain or a dry well, where the whole point is water moving through the voids. Putting the wrong one in either place produces a driveway that never firms up, or a drain that clogs. Size is quoted by grading designations that differ between quarries and states, so describe the use to your supplier — driveway base, top dressing, drainage, walking path — rather than asking for a number you read online.

A gravel surface that lasts is rarely one layer of stone dumped on dirt. A driveway is normally built as a compacted base course of larger crushed stone, placed and compacted in lifts rather than all at once, with a finer top course over it. Each layer is calculated separately here — run the calculator once per lift, using that lift's depth. Compacting in shallow lifts is what makes the difference between a base that holds and one that shifts; a thick layer dumped in one go does not compact all the way down. Under the base, a geotextile fabric separates stone from soil. Without it, the bottom of the gravel gradually presses down into the subgrade and the subgrade pumps up into the gravel, and within a few seasons a good part of what you paid for has effectively disappeared into the ground. Fabric is cheap relative to the stone above it. Edging matters more with gravel than with any other surface, because gravel has no cohesion and will keep moving outward under traffic until something stops it. Finally, remember what gravel does to water. It is more permeable than pavement, which is a genuine stormwater advantage, but a compacted base with fines sheds water much like a hard surface does. Grade the area so runoff goes somewhere you have chosen. Larger paving and driveway projects can also fall under local stormwater or permit rules, so check locally before regrading a significant area.

Two practical points that catch people out on the first order. First, a cubic yard of gravel is genuinely heavy — on the order of a ton and a half at the density above. That figure exceeds the payload rating of many half-ton pickups, and an overloaded truck brakes and steers badly. Check your vehicle's payload rating on the door jamb sticker before deciding to haul it yourself, and remember that a supplier's loader operator will happily put a full yard in the bed if you ask for it. Delivery is usually the right answer past a very small quantity, and suppliers set minimum loads and charge for undersized deliveries, so ask what the minimum is. Second, plan the drop. A dump truck needs room and overhead clearance, and it puts the whole load in one cone. Every shovelful then moves by wheelbarrow, so where the pile lands determines how much of your weekend the job takes. On health: crushed stone contains crystalline silica, and dry cutting, sweeping or working with dusty aggregate can release respirable dust that is a recognized lung hazard. Wet the material down, avoid dry sweeping it, and use appropriate respiratory protection when cutting stone or working in a cloud of dust.