Patio paver calculator
A paver patio is about 7½ inches deep and the pavers are 2⅜ of it. Everything else is base, and base is ordered by volume at a depth it will not stay at — which is why paver jobs run short.
Your patio
How this is calculated
- Pavers = ⌈area × (1 + waste) ÷ paver area⌉.
- Base, compacted = area × depth ÷ 12 ÷ 27, in cubic yards.
- Base to order = compacted × 1.25, because aggregate compacts about 20% and yards sell it loose.
- Sand = area × sand depth ÷ 12, in cubic feet.
- Edge restraint = perimeter length, which is what holds the field together.
Worked example
20 × 12 ft patio, 12×12 pavers, 7% waste, 4″ base, 1″ sand:
- Area = 240 sq ft; pavers = ⌈240 × 1.07 ÷ 1⌉ = 257
- Base compacted = 240 × 4 ÷ 12 = 80 ft³ = 2.96 yd³
- Base loose = 2.96 × 1.25 = 3.70 yd³ — order 4
- Sand = 240 × 1 ÷ 12 = 20 ft³ (40 bags)
- Edge = 2 × (20 + 12) = 64 ft
The gap between 2.96 and 3.70 is 0.74 cubic yards — about a ton of aggregate. That is the difference between finishing and going back for more.
Why the base is the whole job
Pavers are a wearing surface. The structure is the compacted aggregate below them, and its job is to spread load and drain water. Three things make it work: it must be excavated to full depth, compacted in lifts of 2–3″ rather than all at once, and confined at the edges. Skip any of those and the pavers move — first a little, then visibly, and no amount of re-sanding fixes it.
Drainage matters as much as strength. A base that holds water freezes, heaves and settles unevenly. On clay, that means excavating deeper and adding a drainage layer, or the patio will be a shallow pond with pavers in it.
What the paver count leaves out
- It does not design the base for your soil. Clay, sand and fill need different depths and different detailing, and a patio on clay without drainage will fail regardless of the numbers here.
- It does not account for slope. A patio must drain away from the house at roughly 1–2%, which changes excavation depth across the area.
- It does not count a soldier course or border. A border is cut from different units and adds both material and labour.
- It does not include polymeric sand for the joints. Budget a further 1–2 lb per 10 sq ft.
Questions people actually ask
How many pavers for a 20x12 patio?
With 12×12 pavers and 7% cutting waste, 257. With 16×16 pavers it is 145, and with 6×9 cobbles it is 685 — the area is the same, the unit is not.
How deep should the base be?
4″ compacted for foot traffic, 6″ where a vehicle will park, and more over poor soil. Depth is about spreading load and draining water, not about the pavers.
Why do I need more base than the finished depth?
Because aggregate compacts. Four inches of finished base needs about five inches of loose material, so ordering 4″ of loose stone gets you a 3¼″ base.
Do I need edge restraint?
Yes. Without it the field spreads outward at the perimeter, joints open, and the pattern loses its lines within a season. Plastic edge with spikes is the usual solution for a patio.
Can I lay pavers on sand only?
For a temporary path, maybe. For a patio, no — sand alone does not spread load, does not drain well when contaminated with soil, and migrates. The compacted aggregate base is the structure.