The Delivery Truck Problem
Dave ordered gravel for his new driveway the way most people do: he guessed. Two tons sounded like a lot. The truck arrived, dumped its load, and the pile covered about half the driveway. A second delivery cost him another delivery fee, another half day waiting, and a week of his project lost. Then his neighbor ordered by cubic yards from a supplier who sold by the ton, mixed up the units, and ended up with a mountain of surplus stone slowly sinking into the lawn. Gravel is one of those materials where the math is trivial and the consequences of skipping it are expensive.
The entire calculation is one formula: volume equals area times depth, converted to cubic yards, converted to tons. Suppliers sell by weight (tons) or by volume (cubic yards), and the bridge between them is the density of your specific gravel type. Get those three numbers right and the truck shows up once, with the right amount.
How the Gravel Formula Works
Measure your area in feet and your depth in inches. Multiply length by width to get square feet, multiply by depth converted to feet (inches divided by 12), and divide by 27, because there are 27 cubic feet in a cubic yard. That gives you cubic yards. Multiply by your gravel's density in tons per cubic yard to get tons.
Dave's driveway, done right, a 20 by 10 foot rectangle at 4 inches deep with standard crushed stone:
| Step | Math | Result |
| Area | 20 ft x 10 ft | 200 sq ft |
| Depth in feet | 4 in / 12 | 0.333 ft |
| Volume | 200 x 0.333 | 66.67 cubic feet |
| Cubic yards | 66.67 / 27 | 2.47 |
| Plus 10% compaction | 2.47 x 1.10 | 2.72 |
| Tons (x 1.45 density) | 2.72 x 1.45 | 3.94 tons |
Two tons was never going to be enough. He needed four. For a quick reference while planning, here is the coverage you get per ton at common depths:
| Depth | Sq ft per ton | Sq ft per cubic yard |
| 2 inches | 120-140 | 160-190 |
| 3 inches | 80-95 | 110-130 |
| 4 inches | 60-70 | 80-100 |
| 6 inches | 40-50 | 50-65 |
Gravel Types and Why Density Matters
Not all gravel weighs the same, and the difference changes your order more than people expect. Pea gravel, the smooth rounded stone used for patios and playgrounds, runs about 1.3 tons per cubic yard. Standard #57 crushed stone, the angular workhorse of driveways and drainage, is about 1.45. Crushed limestone pushes 1.5, while bank gravel and decomposed granite sit lower around 1.25 to 1.35.
Choose the material for the job first, then use its density. Driveways want angular crushed stone that locks together under tires; rounded pea gravel migrates and ruts under cars. Patios and walkways are the opposite: pea gravel or decomposed granite feels better underfoot. French drains need clean #57 stone with no fines so water flows through. Picking the wrong stone is a more expensive mistake than miscalculating the amount. If your project involves pouring a slab instead, our concrete calculator handles that math the same way.
Depth, Compaction, and the 10% Rule
Depth depends on use. Garden paths and patios need 2 to 3 inches. Residential driveways need 4 to 6 inches, ideally in two layers: a coarse crushed stone base for structure with a finer top layer for a smooth driving surface. Heavy equipment areas and new construction pads can need 8 to 12 inches over prepared soil with landscape fabric underneath to stop the stone from sinking into mud.
Whatever you calculate, add 10 to 20% for compaction and waste. Gravel settles under its own weight, rain washes fines downward, and edges spill during spreading. Ordering exactly the calculated volume guarantees a shortfall. It is far cheaper to have half a ton left over for future touch-ups than to pay a second delivery fee. For irregular areas, break the shape into rectangles, circles, and triangles, calculate each in the tool, and add the results.
How to Use This Calculator
Pick your area shape: rectangle, circle, or triangle. Enter the dimensions and depth in your preferred units (feet, yards, or metric; our unit converter can help if your tape measure reads in centimeters). Choose your gravel type for the correct density, or enter a custom density from your supplier's spec sheet. Set a compaction allowance, defaulting to 10%, and optionally enter your price per ton or per cubic yard for a cost estimate. The calculator returns cubic yards, tons, pounds, the number of 50-pound bags if you are buying retail, and the full step-by-step math so you can check it.
Frequently Asked Questions
How much gravel do I need for a driveway?
Length x width x depth in feet, divided by 27, times about 1.45 tons per cubic yard, plus 10% for compaction. A 20 by 10 foot driveway at 4 inches needs roughly 3.9 tons. Measure twice; delivery fees punish reorders.
How many tons is a cubic yard of gravel?
About 1.3 tons for pea gravel, 1.45 for standard crushed stone, and 1.5 for crushed limestone. Because suppliers may sell by either unit, always convert with your specific material's density instead of guessing.
How deep should gravel be for a driveway?
Four to 6 inches compacted, in two layers if possible: coarse base stone with finer stone on top. Walkways need only 2 to 3 inches. Put landscape fabric under the base on soft soil.
Should I add extra gravel for compaction?
Yes, 10 to 20% over the calculated volume. Gravel compacts, settles, and spills at the edges. Leftover stone is useful for future repairs; a shortfall means paying for another delivery.
How do you calculate gravel for a circular area?
Pi times radius squared times depth, all in feet, divided by 27 for cubic yards. Select the circle tab above and enter the diameter; the calculator handles the rest, including triangles for odd corners.