How much gravel under a concrete slab?
A 4 inch compacted base of crusher run under a 10 × 10 ft slab, extended 6 inches past each edge, is 1.49 cubic yards in place. At about 1.9 tons per compacted cubic yard plus 5% waste, order 2.98 tons, about 3 tons.
How to work it out
- 11 ft × 11 ft = 121 sq ft × 4 in = 1.49 cu yd compacted
- × 1.9 tons per compacted cu yd + 5% = 2.98 tons
- Loose, as delivered: 2.98 tons ÷ 1.52 tons/cu yd = 1.96 cu yd
A 10 × 10 slab is the patio, hot-tub pad or shed floor most people start with. The base below it takes nearly as much planning as the concrete and, by weight, almost as much material.
Adjust for your project
More options: Waste
- Compacted volume in place
- 1.49 cu yd (40.3 cu ft)
- Loose volume (as delivered)
- 1.96 cu yd
- Base area
- 121 sq ft
- Compact in layers of a few inches with a plate compactor, dampening crusher run so it packs. A soft or wet subgrade under the stone needs fixing first — gravel won’t bridge it.
Crusher-run base under a 10×10 slab (6 in overhang) by depth
| Base depth (compacted) | Stone to order | Compacted volume in place | Loose volume (as delivered) |
|---|---|---|---|
| 2 in | 1.49 tons | 0.75 cu yd | 0.98 cu yd |
| 3 in | 2.24 tons | 1.12 cu yd | 1.47 cu yd |
| 4 in | 2.98 tons | 1.49 cu yd | 1.96 cu yd |
| 6 in | 4.47 tons | 2.24 cu yd | 2.94 cu yd |
Why the base is 11 × 11
Running the stone 6 in past every side of the forms gives the slab edges something solid to sit on and keeps the form stakes in firm ground. That turns a 100 sq ft slab into a 121 sq ft base, adding about a fifth to the stone. If your forms sit tight against an existing edge, set the overhang to 0 and the base drops to about 2.46 tons.
In place, 4 in over 121 sq ft is 40.3 cu ft, or 1.49 cubic yards. Crusher run weighs about 1.9 tons per compacted yard (WisDOT gives 1.75–2.1), so the base is 2.84 tons before waste. Delivered loose, it fills about 1.96 yards of truck bed, because it loses a fifth or more of its volume when compacted.
Bulk or bags?
Three tons is a small bulk delivery — many yards have a minimum around that size anyway — and far cheaper than bags. Compact it in two lifts of about 2 in with a rented plate compactor, wetting it lightly so the fines bind. Then build the forms and pour: how much concrete for a 10×10 slab has the concrete, and how many yards of concrete for a 24×24 slab shows a bigger base where a truck delivery is the only sensible option.
Different size? Use the full Gravel Base Under Slab Calculator.
What you’ll need
- Hand tamperBudget price
Compacts gravel base in small areas and post holes. For a full slab base, rent a plate compactor.
See options on Amazon (opens in a new tab) - Square-point shovelBudget price
Pushes and places concrete, and loads sand and gravel. The flat blade spreads a pour better than a round-point shovel.
See options on Amazon (opens in a new tab) - Contractor wheelbarrowMid-range price
A 6 cu ft steel or poly tray with a pneumatic tire moves concrete from the mixer to the forms. Never load it to the brim with wet concrete.
See options on Amazon (opens in a new tab)
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Frequently asked questions
How much gravel under a 10×10 slab with no overhang?
2.46 tons of crusher run at 4 inches compacted, with 5% extra.
How much #57 stone under a 10×10 slab?
About 2.3 tons at 4 inches with a 6 inch overhang, or 1.79 cubic yards loose.
How much gravel under a 12×12 slab 6 inches deep?
About 6.24 tons of crusher run, base extended 6 inches all round.
Sources
- Wisconsin DOT research report 0092-22-05 — Weight-volume relationships and conversion factors for soils and aggregates (2024) (opens in a new tab) — Compacted dense-graded base: 1.75–2.1 tons per cubic yard (Table 1.2).
- FHWA-HRT-15-034 — Strength characterization of open-graded aggregates for structural backfills (opens in a new tab) — No. 57 stone: 95.4 pcf loosest, 108.7 pcf vibrated dry unit weight (Table 7).
- Quikrete Concrete Mix (No. 1101) data sheet (opens in a new tab) — Yields: 40 lb ≈ 0.30, 50 lb ≈ 0.375, 60 lb ≈ 0.45, 80 lb ≈ 0.60, 90 lb ≈ 0.675 cu ft; unit weight ≈ 140 lb/cu ft; for pours 2 in thick or more; 6–9 pints of water per 80 lb bag; control joints every 6–8 ft; cure 5 days at 70 °F or above, 7 days at 50–70 °F; protect from freezing for 48 hours.