How to use
- Enter the patio's length and width, or its total area.
- Choose a paver size, or type in the actual size from the label. Pick the joint width and laying pattern.
- Choose what the paving is for to set the base depth, then select "Calculate".
How the paver count works
Each paver takes up its own size plus one joint on two sides. Pieces per square foot = 144 ÷ ((length + joint) × (width + joint)), with sizes in inches. Multiply by your area, then add extra for cuts.
Example: a 12 ft by 10 ft patio (120 square feet) with 4 × 8 pavers that actually measure 3.94 × 7.87 inches, laid with 1/8 inch joints. Each paver covers (7.87 + 0.125) × (3.94 + 0.125) = 32.5 square inches, so you need 4.43 pavers per square foot, or about 532 for the patio. With 5% extra, order 559. The 6-inch gravel base is 60 cubic feet (2.22 cubic yards, about 4.1 tons), and the 1-inch sand bed is 10 cubic feet, or 20 bags of 0.5 cubic feet.
If the label tells you how many pieces cover a square foot, or gives pieces and square feet per pallet, enter that instead. It's more accurate than working from the size.
Base depth by use
| Use | Compacted gravel base |
|---|---|
| Patios and walkways | 6 to 8 inches |
| Pool decks | 6 to 12 inches |
| Driveways | 10 to 14 inches |
These ranges are from Unilock's installation guide, which calls for 3/4 inch crusher run or clear stone, compacted in layers 2 to 3 inches thick. Clay soil needs the deeper end of the range; sandy soil can use less. The calculator's presets use the shallow end (6 inches for a patio, 10 for a driveway), so go deeper if your soil is soft or drains poorly.
Bedding sand and joints
- Pavers are set on a screeded bed of coarse sand about 1 inch thick, according to both Unilock and the Interlocking Concrete Pavement Institute (ICPI).
- ICPI's construction tolerances call for joints from 1/16 inch to 3/16 inch wide on standard pavers. The calculator defaults to 1/16 inch, which gives a slightly higher, safer count.
- Joint sand is swept in after the pavers are compacted. Coverage depends on the brand and the joint width. Alliance, for example, lists about 65 to 85 square feet per 50 lb bag of G2 Maxx in joints 1/8 to 3/8 inch wide, and Quikrete lists 16 to 64 square feet for PowerLoc. Enter your bag's figure to get a count.
Extra for cuts
Every edge and corner needs cut pavers, and some break. Simple running bond needs the least extra. Herringbone and anything laid at 45 degrees create far more cuts. The pattern presets (5%, 10%, 15%) are common rules of thumb from estimating guides, not a manufacturer requirement. Add more for curves, small areas, or lots of obstacles.
Buying tips
- Buy all your pavers from the same production run if you can. Color can vary between batches.
- Keep a few spare pavers for future repairs.
- Ask whether the supplier charges a deposit on pallets and whether unopened pallets can be returned.
- Base gravel and sand are much cheaper in bulk. The 0.5 cubic foot bag count is there for small jobs and touch-ups.
Common mistakes
- Using the nominal size. A "4 × 8" paver is usually smaller than 4 × 8 inches. Measure one or read the label.
- Skimping on the base. Treat Unilock's depths as the minimum to plan for, and go deeper on clay or wet ground. Compact the base in layers 2 to 3 inches thick.
- Forgetting the edges. Unilock notes that edge restraints are critical and must be spiked into the compacted base. The calculator shows the perimeter so you can buy enough.
- Grading toward the house. Slope the patio away from the building so water drains off.
Sources
Base depths, compaction layers, bedding sand, and edge restraints: Unilock Project Planning Guide. Joint width and bedding thickness: ICPI (now the Concrete Masonry & Hardscapes Association) Construction Tolerance Guide. Holland paver size: Belgard Holland product listing (7.87 × 3.94 in). Joint sand coverage: Alliance Gator G2 Maxx and Quikrete PowerLoc product information. Base weight: Wisconsin DOT conversion for compacted dense-graded base. Sand weight: Quikrete All-Purpose Sand (50 lb, about 0.5 cu ft).
Related calculators
- Gravel Calculator - gravel for paths, pads, and driveways
- Retaining Wall Calculator - a block wall beside your patio
- Mulch Calculator - finish the beds around the patio
- Sales Tax Calculator - add tax to your materials list
Frequently asked questions
How many pavers do I need per square foot?
It depends on the paver size and joint width. Divide 144 by the paver's length plus the joint, times its width plus the joint, all in inches. A 4 × 8 paver that actually measures 3.94 × 7.87 inches, with 1/8 inch joints, works out to about 4.4 per square foot.
How deep should the gravel base be under pavers?
Unilock's guide calls for 6 to 8 inches of compacted gravel for patios and walkways, 6 to 12 inches for pool decks, and 10 to 14 inches for driveways. Use more on clay soil.
How much sand goes under pavers?
About 1 inch of coarse bedding sand, screeded flat over the compacted base. For a 120 square foot patio, that's 10 cubic feet, or about half a ton.
How much extra should I order for cuts?
A common rule of thumb is 5% for running bond and other simple patterns, 10% for herringbone at 90 degrees, and 15% for patterns laid at 45 degrees. These are estimating rules, not a standard, so add more for curves and small areas.
How many bags of polymeric sand will I need?
Check the bag, because coverage varies widely by brand and joint width, from under 20 to more than 80 square feet per 50 lb bag. Enter the figure from your bag and the calculator counts the bags for your area.