Driveway gravel calculator

How this is calculated

1. Driveway areas are summed and multiplied by depth: volume = total area × depth (at depth d inches, cubic yards = square feet × d ÷ 324).
2. If the depth you entered is the loose lift — the cited case — that volume is the order. Running the measured expansion backwards, finished = lift ÷ (1 + 36–47 %), shows what it rolls down to.
3. If instead you entered a finished compacted thickness, the loose volume to buy is finished × (1 + 36–47 %), shown as its own line.
4. Tonnage = compacted, in-place volume × 1.75–2.1 tons per cubic yard — a compacted unit weight, so it is always billed against in-place volume, whichever way you entered the depth.

Data used, with sources

Tons here means US short tons (2,000 lb).

WHRP-measured compacted→loose expansion for Dense Graded Base ¾-inch is 36–47 %. It applies only when you start from a FINISHED compacted thickness and need to know how much loose material to buy. The cited 6–8 in driving-surface lift is already an uncompacted depth, so adding the allowance on top of it double-counts and over-orders by roughly 40 %.

Not every stone is a driving surface

The most expensive driveway mistake is buying the wrong product, and it is easy to make because the wrong products sit in the same yard at a similar price. PennDOT's LTAP sheet names them. Clean, uniformly graded stone — AASHTO 8, 57, 67 — was developed as a structural aggregate for concrete and asphalt; on a driveway it never crusts, so it stays loose, migrates under tyres, and rolls to the edges. Well-graded subbase materials like 2A, 2A Modified and 2RC are the opposite problem: they were designed to sit under a surface, not to be one. Rounded stone is further out still: the pea gravel calculator deliberately applies no compaction factor, because uniform rounded stones roll instead of locking together.

What works is a dense-graded crushed stone carrying enough fines to bind. Pennsylvania's driving-surface aggregate specification is precise about it: 1½-inch top size, 65–97 % passing ¾ inch, 11–15 % passing the #200 sieve, and a plasticity index no higher than 4 — fines from crushed rock, never added clay or silt. Ask your quarry for their driving-surface or road-surface product and what its gradation is; "driveway gravel" is a sales name, not a specification.

Depth, and the double-counting trap

Both cited sources give the same depth and both are explicit that it is the loose material as spread: 6 to 8 inches in a single lift, before the roller touches it. That matters for ordering, because it means the number already contains the expansion. A calculator that takes 6 inches and then adds "20 % for compaction" is charging you for the same air twice — with the measured 36–47 % expansion for graded base, the error runs to roughly 40 %.

The allowance is real, it just points the other way. If your plan specifies a finished thickness — a compacted 4-inch surface, say — then you do need to buy 36–47 % more loose material than that finished volume. Tell the calculator which of the two you typed and it applies the correction in the right direction, or not at all.

Below the surface course, we publish no number. The NRCS standard's shortcut thickness is scoped to light non-vehicular use, and for vehicle traffic it points to a design procedure that needs your subgrade strength, traffic and frost depth. A soft or wet subgrade can swallow far more stone than any table would predict, and that is a site question, not an arithmetic one. If your plan does specify a finished base thickness, the crushed stone calculator applies the compaction allowance to it in the right direction.

Common mistakes

• Adding a compaction allowance to the 6–8 inch figure. It is already an uncompacted depth. Add the allowance only to a finished thickness.
• Buying #57 or clean stone for the surface. It cannot crust, so it never stops moving. Cited guidance rules it out as a driving surface.
• Using subbase stone as the wearing course. 2A and 2RC are well graded and strong, but they were developed to go underneath one.
• Building it flat. The driving-surface spec calls for a crown or cross slope of ½ to ¾ inch per foot. Water that cannot run off runs through, and takes the surface with it.
• Spreading it in thin layers over several deliveries. The cited practice is a single 6–8 inch lift, compacted as one.
• Treating the tonnage as exact. The conversion is a published range, and pay-by-ton orders settle on the quarry's scale ticket.

Frequently asked

Sources

• Weight-Volume Relationships and Conversion Factors for Soils and Aggregates of Wisconsin (WHRP G22-05) — Wisconsin Department of Transportation / Wisconsin Highway Research Program, accessed Aug 11, 2026.
• Driving Surface Aggregate Standard and Specification (rev. 18 March 2025) — Pennsylvania State Conservation Commission / Penn State Center for Dirt and Gravel Road Studies, accessed Aug 11, 2026.
• Technical Information Sheet #186: Maintenance of Gravel Roads (J. A. Snyder, P.E., Winter 2017) — PennDOT Local Technical Assistance Program (LTAP), accessed Aug 11, 2026.
• Conservation Practice Standard: Heavy Use Area Protection (Code 561), September 2020 — USDA Natural Resources Conservation Service, accessed Aug 11, 2026.