The two layers under your pavers
A paver patio that stays flat for years isn't really about the pavers themselves — it's about what's underneath them. There are two separate layers, and they do two different jobs.
The gravel baseis the structural layer. It's crushed stone, spread and compacted in lifts (usually 2 in at a time), and its job is to spread out the weight sitting on top of it and let water drain away instead of pooling under the patio. This is the layer that actually keeps the ground from shifting or heaving underneath your pavers.
The bedding sandon top is a thin leveling layer — about 1 inch, screeded flat — that the pavers actually sit in. Its only job is to let you set each paver at a precise, even height. It's not there to bear weight or add strength, which is why it should never be thicker than about 1–1.5 inches: a deeper sand bed is soft and compresses unevenly, so pavers laid in it will rock, sink, or drift out of alignment over time. If your project needs more height, add it to the compacted gravel base instead, never to the sand.
The formula and a worked example
Both layers use the same volume formula — only the depth and the material density change:
Cubic feet = Length × Width × (Depth in ÷ 12) × (1 + waste %)
Cubic yards = Cubic feet ÷ 27
Tons = Cubic yards × density (1.4 for gravel base, 1.35 for sand)
Worked example: a 12 ft × 10 ft patio, with a standard 4 in gravel base and 1 in bedding sand, and the default 10% waste allowance:
Base: 12 × 10 × (4 ÷ 12) × 1.10 = 44 ft³ → 44 ÷ 27 ≈ 1.63 yd³ → 1.63 × 1.4 ≈ 2.3 tons
Sand: 12 × 10 × (1 ÷ 12) × 1.10 = 11 ft³ → 11 ÷ 27 ≈ 0.41 yd³ → 0.41 × 1.35 ≈ 0.6 tons (22 bags at 0.5 ft³ each)
Add the two together and that patio needs about 2.8 tons of material total — roughly 2.3 tons of crushed stone for the base and 0.6 tons (or 22 bags) of sand for the bedding layer. The waste allowance covers spillage and the fact that compaction settles loose material, so ordering exactly the raw volume tends to come up short on-site.
What sand to use under pavers
Ask for coarse concrete sand— often labeled "bedding sand" or "paver sand" at landscape supply yards — not play sand or fine mason's sand. Play sand is washed round and smooth for sandboxes, which means it doesn't compact or lock together, so pavers set in it can shift and rock. Concrete sand's sharper, angular grains interlock under compaction and drain well, which is exactly what a bedding layer needs to do.
Don't confuse bedding sand with polymeric sand. Bedding sand goes down first, in a roughly 1 in layer under the pavers, and this calculator sizes that layer by area. Polymeric sand is a completely separate product — a fine sand blended with a binder — that gets swept into the joints between pavers after they're laid, then activated with water so it hardens and locks the joints against weeds and ants. It's bought separately, by the bag, sized to your joint width and paver count rather than your patio's square footage.
How much to excavate
Excavation depth is the sum of everything going back into the hole, minus how high you want the finished patio to end up above the surrounding grade:
Excavation depth = base depth + sand depth + paver thickness − final height above grade
For example, a 4 in gravel base plus 1 in bedding sand plus a 2.375 in (60 mm) paver adds up to 7.375 in of total buildup. If you want the finished patio sitting about 1 in above the surrounding lawn — typical, so water sheds away from it — you'd excavate roughly 6.4 in deep. It's worth digging a little extra beyond the math, since compacting the base and sand also settles them slightly below their loose-poured depth.