Pavers get the attention, but the base underneath is usually the largest order by volume. The calculation is a box: the patio’s area times the depth of base.
Base volume (cu ft) = patio area (sq ft) × base depth (ft)
Depth in feet = depth in inches ÷ 12
Volume (cu yd) = cu ft ÷ 27
Order = volume × (1 + allowance)
The depth is your decision
How deep the base should be depends on the soil, the climate, how the patio will be used and the paving system. Belgard’s technical guide, for example, gives minimum base thicknesses that depend on use and says freeze-thaw climates and site conditions can call for more. This guide does not choose a depth for you. It shows what a depth does to the quantity.
A 12 × 16 ft patio at two example depths
The two depths below are examples only. They are not recommendations for your site.
| Base depth | Volume | With 10% allowance |
|---|---|---|
| 4 in (example) | 2.37 yd³ (4 in layer) | 2.61 yd³ |
| 6 in (example) | 3.56 yd³ (6 in layer) | 3.91 yd³ |
This example assumes
- A 192 sq ft patio
- The base volume shown before any allowance, then the planner’s 10% allowance for base and bedding
- Allowance is an editable planning default
Six inches takes 1.5 times the volume of four, because depth is the only thing that changed. With no allowance at 6 inches the base is 3.56 yd³, against 3.91 yd³ with the 10% allowance.
Why there is an allowance
Aggregate is compacted in place, so the loose material you order is more than the finished layer holds, and an uneven subgrade swallows extra. The allowance covers some of that. It is a planning default that you can change when you know better.
Cubic yards or tons
Base aggregate is often sold by weight, and the weight of a cubic yard depends on the material. The tons versus cubic yards guide explains the conversion, and why your supplier’s figure is the one to use.
What changes the estimate?
- The base depth you choose for your installation
- Patio area, including any border or step
- The allowance for compaction and uneven ground
- Whether the material is ordered by volume or weight