Base Rock Calculator

Base rock is ordered loose but specified compacted — this calculator bridges the two. Enter your area and target compacted depth and get the loose volume and tons to actually order.

Base Rock Details

Length

Width

Compacted Depth

Compaction Factor (loose material needed)

Base rock compacts down, so you order more loose material than the final depth

Base Rock Density

tons/yd³

Enter your area and compacted depth to see loose base rock needed.

The formula

Loose yd³ = (L × W × Depth ÷ 12) ÷ 27 × (1 + Compaction %) → Tons = Loose yd³ × Density

The compaction allowance (default 15%) is the key difference from a plain gravel calculation: a 4-inch compacted base needs roughly 4.6 inches of loose material spread first. Density defaults to 1.5 tons/yd³, typical for crushed base rock and crusher run.

Placement tips

Compact in lifts — 2 to 4 inches of loose material at a time — rather than trying to compact a thick layer in one pass. Lightly wetting the material before compaction helps particles seat. A plate compactor handles patios and walkways; drives and pads warrant a roller or repeated passes.

Frequently Asked Questions

How much base rock goes under a patio?

4 inches compacted is typical for paver patios and walkways; 6 inches or more for driveways. Enter your compacted target and the calculator adds the loose-material allowance.

What is crusher run?

Crushed rock graded from a top size (like 3/4 in) down to fines. The fines lock the layer together under compaction, which is why it’s the standard base material.

Do I really need to order 15% extra?

Yes — that extra is consumed by compaction, not wasted. Ordering the geometric volume of the finished base means a short load.