By weight
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Sub-base
Gravel base calculator
Size the crushed-stone sub-base under your slab — in cubic yards and tons, with a compaction allowance built in.
Sub-base
FIG. 01required
required
required
Crushed stone compacts when tamped, so order extra. Aggregate is sold by the ton as well as the yard — both are shown.
You need
—cu yd
Order to nearest ½ yd → —
Cubic feet
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How this is calculated
Multiply the area by the base depth (4 inches is standard, 6 over soft soil), convert to cubic yards, and add ~10% because crushed stone compacts when tamped. This calculator also converts to tons, since aggregate is often sold by weight.
cubic yards = (length × width × depth in ft) ÷ 27 × (1 + compaction%) · tons = cubic yards × 1.5
Then pour on top with the slab calculator. See methodology for the density assumption.
FAQ
How much gravel do I need under a concrete slab?
Multiply the area by the base depth (4 inches is standard, 6 over soft soil), convert to cubic yards, and add ~10% because crushed stone compacts when tamped. This calculator also converts to tons, since aggregate is often sold by weight.
How many tons of gravel in a cubic yard?
Crushed stone runs about 1.5 tons per cubic yard (~3,000 lb). So a 20 × 20 ft, 4-inch base — about 5.4 cubic yards with compaction — is roughly 8.1 tons.