How Much Gravel for a Patio Base? Depth and Tonnage Math
A tape measure speaks in feet. The quarry speaks in tons. Nothing on my sketch of the backyard said anything about weight, and nothing on the supply yard’s price sheet said anything about square footage. Bridging those two languages is the entire job of ordering a patio base, and it comes down to three conversions: feet to cubic feet, cubic feet to cubic yards, and cubic yards to tons. I’ll walk through all three using a real project — a 10 by 20 foot paver patio with 4 inches of compacted crushed stone underneath — and tell you about the delivery truck that idled in my driveway while I figured out the last conversion on the phone.
Step one: feet to cubic yards
The footprint is easy. Ten feet by twenty feet is 200 square feet. Depth is where people slip, because gravel depth is quoted in inches and volume math wants feet. Four inches divided by 12 is 0.333 feet.
Multiply the two and you get the compacted volume: 200 sq ft × 0.333 ft = 66.7 cubic feet. Bulk suppliers sell by the cubic yard, and a cubic yard is 27 cubic feet, so 66.7 ÷ 27 = 2.47 cubic yards of compacted stone. If you’d rather not chase decimals across a notepad, our mulch and gravel calculator runs the same length × width × depth math and spits out yards directly.
That 2.47 figure is correct and also not what you should order. Read on.
The compaction allowance the price sheet never mentions
Crushed stone comes off the truck loose and fluffy, full of air gaps. A plate compactor squeezes those gaps shut, which is the whole point of a base layer — and it means the pile shrinks. To end up with 4 inches of compacted stone, you need to spread roughly 5 inches of loose stone, because loose material loses about a fifth of its volume under compaction.
The standard allowance is 20–25% extra loose material. Applied to our patio: 2.47 yards × 1.20 = 2.96 yards on the low end, and 2.47 × 1.25 = 3.09 yards on the high end. In practice you order 3 cubic yards and stop worrying about it. Three yards is 81 loose cubic feet, which lands almost exactly on the 80 cubic feet the 20% allowance calls for, with a small cushion for the stone that inevitably ends up in the lawn.
Skip this allowance and you’ll compact your way to a base that’s a half-inch to an inch shy of plan, then pay a second delivery fee to fix it. The allowance costs less than the truck.
Yards to tons, because that’s how the quote arrives
My supply yard, like most, prices crushed stone by the ton, not the yard. The bridge between the two is bulk density, and suppliers publish typical figures: crushed stone runs about 1.5 tons per cubic yard, pea gravel about 1.4, while shredded mulch is only about 0.4. Stone is nearly four times as heavy as mulch for the same size pile, which is exactly why mulch quotes come in yards and stone quotes come in tons.
So the patio order converts like this: 3 cubic yards × 1.5 tons/yard = 4.5 tons of crushed stone. As a cross-check, one ton of crushed stone works out to 18 cubic feet (27 ÷ 1.5), which covers about 54 square feet at a 4-inch depth. Divide 200 sq ft by 54 and you get 3.7 tons compacted; add the 20–25% loose allowance and you’re back at 4.4 to 4.6 tons. Two routes, same answer — that’s how you know the math is holding together.
The awkward phone call
The yards-to-tons step bit me on this exact patio. For it I called the yard and ordered “three yards of three-quarter-inch crushed stone,” hung up feeling organized, and went back to staking the layout. Two days later the driver handed me a delivery ticket that read 4.6 TN @ $45.00/TN — $207.00, and my stomach dropped. I had three yards in my head and 4.6 of something else on paper, and it looked for all the world like they’d brought me half again too much rock.
So I called the yard while the driver waited with the bed half-raised. The woman at the desk read me the conversion chart taped to her counter: crushed stone, about 1.5 tons per yard. 4.6 tons ÷ 1.5 = just over 3 cubic yards — precisely my order, weighed on the truck scale rather than measured by the bucket. The extra tenth of a ton was loader slop and a damp night’s worth of water weight, both normal. Total call time, four minutes. Total damage to my pride, considerably more. The chart now lives as a photo on my phone, and the conversions above are why you won’t need one.
What the whole base cost
The numbers from my ticket, for reference: 4.6 tons at $45 per ton came to $207, plus a $60 delivery fee, for $267 total — about $1.34 per square foot of patio, before a single paver goes down. Crushed stone pricing swings a lot by region and haul distance, so treat my $45 as one data point from one yard, not a benchmark. The structure of the math is what transfers: tons × price per ton + delivery.
Bags versus bulk at this size
Bagged gravel exists, and for a 200-square-foot base it’s the wrong tool. You need 81 loose cubic feet; if the bag on the shelf lists 0.5 cubic feet, that’s 162 bags to load, haul, and lift twice. Whatever bag size you find, divide 81 by it and let the answer make the argument for bulk delivery. If you want a feel for how fast bag counts balloon, the same logic drives how many bags fit in a cubic yard — and gravel bags are heavier than mulch bags by a wide margin.
Where the calculator’s job ends
Everything above is quantity math, and that’s deliberately all it is. How thick your particular base should be, whether you need fabric under it, how to compact it in lifts, what your soil and frost line demand — those are construction decisions that depend on your site, and a materials calculator has no business making them. Get the base spec from your paver manufacturer’s instructions or a local supplier who knows your ground, then bring that depth number back to the math here. I ran this example at 4 inches because that’s what my project called for; yours may differ, and the formulas don’t care.
One honest note on precision: stone density isn’t a constant of nature. Moisture, rock type, and how the load settles all nudge the tons-per-yard figure, so your delivery ticket may land a tenth of a ton off the chart math, the way mine did. Order with the 20–25% allowance built in and those wobbles disappear into the cushion. When you’re ready to price the next bed or path, the gravel volume calculator handles the feet-to-yards legwork in one pass — the tons, you can now do on the back of the quote.