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SlabCosts
Prices updated January 2026

Gravel Calculator

The compacted gravel base under your slab — how many cubic yards to order, and what it costs.

Gravel base calculator

You need

5.68 yd³

153.3 ft³ (compacted order)

Estimated cost $170 – $369
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Sizing the gravel base

A compacted gravel base spreads the load and lets water drain away from the underside of your slab. Because you buy gravel loose but place it compacted, you need to order a little extra — this calculator adds about 15% so you're not caught short.

Came here from the slab calculator? Your width and length are already filled in. Head back to the slab calculator to finish the pour.

Prices updated January 2026 National US averages · reviewed quarterly

Volumes use standard bag yields and a 10% waste allowance; costs are national US averages that vary by region, mix and finish. See our methodology for exactly how each figure is worked out, or check the reference sources:

Concrete calculators

Frequently asked questions

How much gravel do I need under a concrete slab?
A 4" compacted gravel base is standard under a slab. Multiply the slab area by 4" (0.333 ft) for the compacted volume, then add ~15% because gravel compacts down — this calculator includes that allowance.
How deep should the gravel base be?
Four inches of compacted crushed stone suits most residential slabs. Poorly draining or frost-prone soils may need more. Set the depth above to match your build.
How much does gravel cost?
Crushed gravel runs about $30–$65 per cubic yard delivered in 2026, plus delivery for small loads.