How to use this calculator
- Choose the project type and base depth. Patios and walkways need less base than driveways.
- Set the bedding sand depth and paver thickness. About 1 inch of sand and 2⅜-inch (60 mm) pavers are common.
- Add the paved area as rectangles or circles at its finished size. The calculator adds the extra base width itself.
Base depth guidelines
| Project | Compacted base |
|---|---|
| Walkway or patio | 4 – 6 in |
| Driveway | 8 – 12 in |
These are Unilock’s guidelines. Choose the deeper end on clay or poorly drained soil, and in climates with hard freezes. Unilock also recommends extending the base past the paver edge by the base depth, so a 6-inch base runs 6 inches beyond the pavers on every side, and compacting it in layers of 3 to 4 inches.
The formulas
- Base footprint = (length + 2 × base depth) × (width + 2 × base depth)
- Base gravel = base footprint × base depth ÷ 12, plus 5–10% for compaction
- Bedding sand = paved area × sand depth ÷ 12
- Dig depth = base depth + sand depth + paver thickness
Worked example
A 16 × 12 foot patio with a 6-inch base, 1 inch of bedding sand and 2⅜-inch pavers:
- Base footprint: (16 + 1) × (12 + 1) = 221 sq ft
- Base gravel: 221 × 6 ÷ 12 = 110.5 cu ft, plus 10% = 121.6 cubic feet, about 4.5 cubic yards or 6.3 tons at 1.4 tons per yard
- Bedding sand: 192 × 1 ÷ 12 = 16 cubic feet, about 0.6 cubic yards
- Dig depth: 6 + 1 + 2⅜ = 9⅜ inches, removing about 6.4 cubic yards of soil
- Compaction: the 6-inch base goes down in 2 layers
Tips for a base that lasts
- Use a dense-graded base such as crushed stone with fines (often sold as road base or crusher run), which compacts firmly. See our gravel calculator for stone weights.
- Slope for drainage. Unilock suggests 1 to 2%, which is about ½ inch of fall over 4 feet at 1%. Slope away from the house.
- Compact the soil first, then each layer of base, wetting it lightly if it is dry.
- Screed the sand, don’t compact it, before laying pavers, then compact the pavers and sweep in joint sand.
Sources
- Unilock: Do’s and don’ts of paver installation, base preparation
- Select Sand & Gravel: How much does a yard of road base weigh?
Frequently asked questions
How deep should the base be for pavers?
Unilock’s guideline is 4 to 6 inches of compacted base for pedestrian walkways and patios, and 8 to 12 inches for driveways. Poorly drained or clay soils and colder climates generally call for the deeper end.
How much wider than the pavers should the base be?
Unilock recommends extending the base beyond the paver edge by the same distance as the base depth. For a 6-inch base, extend it 6 inches past the edge on every side.
How thick should bedding sand be under pavers?
About 1 inch of bedding sand is typical, screeded smooth over the compacted base. Don’t use the sand to fix low spots in the base; level the base itself.
How deep do I need to dig for a paver patio?
Add the base depth, the bedding sand and the paver thickness. For 6 inches of base, 1 inch of sand and 2⅜-inch pavers, dig about 9⅜ inches below the finished surface.
How do I compact a paver base?
Spread and compact the base in layers. Unilock notes that typical plate compactors only compact about 3 to 4 inches at a time, so a 6-inch base needs at least two layers.