How to measure for aggregate
Measure the area in feet and decide on a compacted depth — the depth after rolling, not the loose depth off the truck. Loose stone compacts roughly 20–30%, so a 4-inch finished driveway needs about 5 inches of loose material. The calculator's default 15% waste factor accounts for this plus normal spillage; bump it to 20–25% for very soft subgrades where stone sinks in.
For French drains, measure the trench: length × width × depth in feet, divided by 27. A 50-foot trench 12 inches wide and 18 inches deep needs about 3.3 yards of drain rock. For paver patios, calculate the base at 4–6 inches deep across the full patio footprint plus 6 inches beyond the edge on all sides.
Choosing the right stone
- Crusher run / 21AA / road base — angular fines-to-1" mix that compacts like concrete. The default choice for driveways and bases.
- #57 / 3/4" clean stone — uniform, no fines. Drains freely; best for French drains, septic, and behind retaining walls.
- Pea gravel — rounded and decorative. Great for beds and pathways, terrible for driveways (it migrates).
- Riprap — large 6–24" stone for erosion control on slopes and shorelines, not a driving surface.
- Decomposed granite — natural pathway material that compacts firm but needs edging to stay put.
Names vary by region — "21AA" in Michigan is "crusher run" in the Southeast. Describe the use (driveway base, drainage) and let the quarry translate.
Installation tips that actually matter
- Fabric first. Woven geotextile under a driveway keeps stone from sinking into soil. It's the highest-ROI $100 in the project.
- Crown it. Grade driveways with a 2% crown (about ¼ inch per foot) so water sheets off instead of ponding and rutting.
- Compact in lifts. For depths over 4 inches, spread and compact in 3–4 inch lifts. A plate compactor rents for $60–$90/day.
- Edge it. Stone migrates without edging. Steel, aluminum, or pressure-treated timber edging keeps driveways and beds crisp.
What affects gravel cost
Bulk aggregate runs $25–$60 per ton at the quarry, with delivery typically $50–$100 per load (a tri-axle carries ~20–25 tons). Bagged stone at retail runs $4–$6 per half-cu-ft bag — over $400 per equivalent yard — so bags are strictly for small repairs.
Installed, a new gravel driveway runs $1.50–$3.50 per square foot including excavation, fabric, and compaction; re-topping an existing drive runs $1–$2 per square foot. Haul distance dominates pricing — a quarry 40 miles away can double the per-ton cost.
Common gravel mistakes to avoid
- Skipping landscape fabric. Without geotextile fabric under the stone, it migrates into the soil within a year or two and you're buying the same load twice.
- Too thin a layer. A 2" scatter over dirt ruts immediately. Driveways need 4–6" compacted; the calculator's depth is the finished depth, not the loose-dump depth.
- Wrong stone for the job. Rounded pea gravel looks great in beds but rolls under tires — driveways and paths want angular crushed stone that locks together.
Gravel FAQs
How do I calculate gravel for a driveway?
Length × width × depth (feet) ÷ 27 = cubic yards; multiply yards by ~1.4 for tons. A 12×50 ft drive at 4 inches needs about 7.4 yards, or 10.4 tons.
How many tons are in a cubic yard of gravel?
About 1.4 tons for typical crushed stone. Dense crusher run can hit 1.6; light decorative stone may be 1.2. Your supplier's scale ticket is the final word.
How deep should a gravel driveway be?
4–6 inches compacted for residential use; 6–8 inches for heavy vehicles or soft soils, placed in two compacted lifts.
Crushed stone or pea gravel for a driveway?
Crushed stone — its angular edges lock together under compaction. Pea gravel is rounded, shifts under tires, and belongs in beds and pathways.
Do I need landscape fabric under gravel?
Yes for driveways and parking pads. Woven geotextile prevents stone from sinking into soil and dramatically extends driveway life.