How this road base calculator works
Base course is bought loose but specified compacted, so the density and the allowance both reflect stone that’s been rolled tight:
tons = yd³ × 1.5 (dense-grade) × (1 + waste%) → rounded up to ¼ ton
At the defaults — a 50 × 12 ft drive, 6 in compacted, 10% allowance — the scale order is 18.5 tons, about $648; the full chain is in the load math section below.
What is dense-grade road base?
Road base is crushed stone with the fines left in — a full gradation from powder up to about ¾–1½ in — so it compacts into a near-solid, load-spreading mat. That’s what separates it from clean stone, and it’s the structural layer under almost every surface:
- Dense-grade base — 1.5 t/yd³ compacted: the standard structural lift, packs tight. The calculator’s default.
- Crusher run / CA-6 — 1.4 loose: the same material priced before compaction — use it when the quarry quotes loose tons.
- #57 clean top course — 1.35: the fines-free wear stone that rides on the base, not instead of it.
- Recycled crushed concrete: compacts like dense-grade at a lower price — the crushed concrete calculator prices that version.
On a gravel driveway the base is the driveway — the loose #57 on top just keeps tires off the fines. The gravel driveway calculator prices all the lifts together; this page sizes the base lift on its own for any project.
How deep should road base be?
Base depth follows the load above and the ground below — heavier surface or softer subgrade, deeper base — and it’s always placed in lifts, never one deep dump. What each job wants:
- Gravel driveway (firm ground): 6–8 in compacted, in 3–4 in lifts.
- Gravel driveway (soft / clay): 8–12 in, often over a geotextile fabric and a large-stone sub-base.
- Under pavers or a concrete slab: 4–6 in of compacted base.
- Under asphalt: 6–8 in — the flexible pavement leans on the base for its strength.
- Always in lifts: place 3–4 in, compact, repeat. One deep loose dump never packs and ruts by spring.
How much road base by driveway size?
Table 1 runs common drives through the engine at 6 in compacted; Table 2 is the full three-lift build a gravel driveway wants.
| Driveway | Base tons |
|---|---|
| 40 × 10 ft | 12.25 t |
| 50 × 12 ft | 18.5 t |
| 100 × 12 ft | 36.75 t |
| 150 × 12 ft | 55 t |
| Lift | What & how deep |
|---|---|
| Subbase | #3 stone, 4–6″ (soft ground) |
| Base | Crusher run / CA-6, 4″ |
| Top | #57 clean stone, 2–3″ |
How to measure for road base
- Measure the driveway length and width along the centerline; add flares and pads as rectangles.
- Set the compacted depth by ground condition — 6 in firm, 8–12 in soft — the depth guide has the ranges.
- Pick dense-grade for compacted tons, or crusher run if your quarry quotes loose; the density differs.
- Leave the allowance at 10% — compaction and spillage; go 15% on rough grade.
- Enter the per-ton price, delivered — road base is cheap, so the haul is a real share of the cost.
Worked example: base for a 50 × 12 gravel driveway
The default, worked line by line — 50 × 12 ft, 6 in compacted dense-grade at 1.5 t/yd³, 10% allowance, $35 a ton:
volume = 600 × (6 ÷ 12) = 300 ft³ = 11.1 yd³
weight = 11.1 × 1.5 = 16.7 tons exact
allowance = 16.7 × 1.10 = 18.33 → order 18.5 tons
cost = 18.5 × $35 = $648 · 1 ton covers 36 ft² at 6″
Road base disappears fast — 18.5 tons for one modest driveway, roughly a full tandem load — because depth times a dense material adds up. Which is exactly why it goes in lifts: you can’t compact 6 in of loose stone in one pass, and stone that isn’t compacted isn’t base, it’s just an expensive rut.
Worth pricing the whole build, not just the base: on a gravel driveway this 18.5-ton base lift is the structural money, but the 2–3 in of clean #57 that tops it and the #3 sub-base under soft ground add their own tons. The gravel driveway calculator stacks all three so the total order lands in one call to the quarry.
What this road base estimate doesn’t include
- The top course. Clean #57 over the base on a gravel drive — a separate order.
- Sub-base. Large #3 stone under the base on soft ground.
- Geotextile fabric. Between subgrade and stone on clay or wet sites.
- Compaction equipment. A plate compactor or, for real length, a roller — non-negotiable for base.
- Excavation and grading. Cutting the lane, shaping the crown, hauling spoil.
- Delivery. A flat per-load fee — a real share of a cheap material.
Road base FAQ
How much road base do I need for a driveway?
A new 50 × 12 ft gravel driveway at 6 in compacted takes 11.1 yd³ — 16.7 tons of dense-grade base, ordered as 18.5 tons with the 10% compaction allowance, about $648 at $35 a ton. Scale the dimensions above to your drive.
How many tons of road base are in a cubic yard?
About 1.5 tons compacted in place — the fines pack the voids solid, which is the whole point of dense-grade. Loose in the truck it runs nearer 1.4; the calculator carries both figures so you can price either way.
How deep should road base be?
6–8 inches compacted for a residential gravel driveway on decent ground, 8–12 over soft or clay subgrade, placed in 3–4 in compacted lifts. Under concrete or pavers, 4–6 in usually does; under asphalt plan 6–8.
What is the difference between road base and gravel?
Road base is crushed stone WITH the fines left in — sizes from dust up to ¾ or 1½ in — so it locks into a hard, almost pavement-like mat. Clean gravel like #57 has no fines, stays loose and drains; it tops the base rather than replacing it.
What is CA-6, Class 5, 21A road base?
Regional names for the same idea — dense-graded aggregate base. CA-6 (Illinois), Class 5 (Minnesota), 21A/21B (Virginia and the mid-Atlantic), ABC (the Southeast) and "crusher run" all describe crushed stone graded from fines up to about ¾–1½ in that compacts into a structural mat. The name on the quarry board is local; the material and this math are the same.
How much does a ton of road base cover?
About 36 ft² at 6 in compacted — 54 ft² at 4 in, 27 at 8 in. Road base goes fast: a single car-width drive eats a ton roughly every 9 feet at full depth.
How much does road base cost?
Typically $25–45 per ton in 2026 — one of the cheapest materials a quarry sells — plus delivery. The default driveway is about $648 in stone; spreading and plate-compacting it is where the weekend goes.
Sources and standards
- ASTM D2940: graded aggregate base for roads — the gradation that compacts dense.
- State DOT base specs (CA-6, Class 5, 21A, ABC): the regional names for dense-grade base.
- 95%-compaction practice: the 3–4 in lift, roll-each-lift method behind the depth guide.
- The scale ticket: compacted vs loose density and moisture move the weight — the quarry ticket governs.
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