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Gravel Driveway Calculator Guide
A gravel driveway isn't one layer of stone. It's three, each doing a different job, and ordering it as a single depth of one product is why so many of them fail.
Cubic feet = length × width × depth ÷ 12 · cubic yards = cubic feet ÷ 27 · tons = cubic yards × density
A 100×12ft driveway at 9in total = 900 cu ft = 33.3 cu yd ≈ 47 tons at 1.4 tons/yd³.
Three Layers, Three Jobs
The sub-base is large angular stone that spreads load and keeps the driveway out of the mud. The base is medium stone that locks into the sub-base and forms the structure. The surface is small angular stone that binds tight enough to drive on.
Skip the sub-base and you get a driveway that looks fine for a season and then develops ruts and potholes, because there's nothing between the traffic and the soil.
Angular, Not Round
Pea gravel and river rock are rounded, so they roll over each other and never lock. They migrate, they rut, and they end up in your lawn.
Crushed angular stone has sharp faces that key into each other and stay put. It's the single most consequential choice on the page and it's not a matter of taste — round stone in a driveway is a mistake that shows up within months.
Order by Weight and Expect Compaction
Stone is sold by the ton, not the cubic yard, so the density figure matters — and it varies by stone type and by supplier. Ask yours rather than trusting a number from the internet.
Loose stone also settles. Ordering the exact finished depth leaves you short once it's rolled, which is what the compaction allowance is for. Coming up short on the last layer is worse than a small surplus, because a second delivery costs a full delivery fee.
Drainage Decides Its Lifespan
Water sitting under a driveway destroys it from below regardless of how much stone you put down.
A slight crown so water runs off the middle, and somewhere for that water to go, matter more than the last inch of depth. A well-drained 6in driveway outlasts a badly drained 12in one.
Geotextile Fabric
On soft or clay ground, fabric between soil and sub-base stops the stone slowly sinking into the earth. It's cheap relative to the stone and it's the difference between topping up every few years and topping up every decade.
Related: gravel calculator for general volume, crushed stone calculator, cubic yard calculator.
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