Paver calculator: pavers, base gravel and sand for a patio

Quick answer

A 12 × 12 ft patio of 4 × 8 in Holland pavers (actual size 3 7/8 × 7 13/16 in) with 1/8 in joints needs about 653 pavers, or 719 with 10 percent extra. On a 4 in compacted base that reaches 6 in past the edges, order about 2.6 cubic yards (3.9 tons) of base material, plus 0.45 cubic yards of bedding sand for a 1 in layer.

What this calculator does

It works out the whole shopping list for a patio of interlocking pavers laid on sand: the number of pavers, the crushed stone for the base, the bedding sand and the length of edge restraint. It handles rectangular patios, round patios and a round patio around a fire pit, where the pit in the middle is not paved.

It does not include the polymeric or jointing sand that fills the joints after laying, geotextile, or the fire pit itself. For the blocks of a fire pit or a garden wall, use the retaining wall calculator. Slabs laid on a full mortar bed are calculated differently: see the notes on UK practice below.

How to use it

1. Choose metric or US units. In US units you can type feet and inches, such as 12' 6", and fractions, such as 7 13/16.
2. Choose the shape and enter the size of the paved area. For a patio around a fire pit, enter the outer diameter of the paving and the diameter of the pit.
3. Enter the actual length and width of one paver and the joint width. The actual size is printed on the pallet label or the product sheet.
4. Choose the laying pattern. It sets the allowance for cuts, which you can change.
5. Check the base thickness, how far the base reaches past the paving, the compaction allowance and the bedding sand thickness. Replace the weights of the materials with the values your supplier gives.
6. Choose whether you need edging, then select Calculate.

How the result is calculated

1. Area: rectangle = length × width; circle = π × (diameter ÷ 2)²; around a fire pit = π × (outer diameter ÷ 2)² − π × (pit diameter ÷ 2)².
2. Area of one paver with its joint = (paver length + joint) × (paver width + joint).
3. Pavers = area ÷ area of one paver with its joint × (1 + allowance ÷ 100), rounded up to a whole paver.
4. Base area: the paved area enlarged by the margin on every side; around a fire pit, only on the outside.
5. Base to order = base area × base thickness × (1 + compaction allowance ÷ 100). Weight = volume × weight of the base material.
6. Bedding sand = paved area × sand thickness. Weight = volume × weight of the sand.
7. Edging = the perimeter of a rectangle or circle; around a fire pit, the outer circumference, because the wall of the pit holds the inner edge.

Weights are shown in tonnes or US short tons of 2000 lb. Volumes to buy are rounded up to 0.01 m³ or 0.01 cubic yard.

Worked example

US units: a patio of 12 × 12 ft is 144 sq ft. A Holland paver of 3 7/8 × 7 13/16 in (entered as 3.875 and 7.813) with a 1/8 in joint takes up 4 × 7.938 = 31.75 sq in. Pavers: 144 × 144 ÷ 31.75 = 653.1, and with 10 percent extra 718.4, so 719 pavers.

Base: 4 in thick, reaching 6 in past each edge, so over 13 × 13 = 169 sq ft: 169 × 4 ÷ 12 = 56.3 cu ft compacted. With 25 percent extra for compaction, 70.4 cu ft, which is 2.61 cubic yards. At 109.3 lb per cu ft that is 7,697 lb, or 3.85 tons. Sand: 144 × 1 ÷ 12 = 12 cu ft, 0.45 cubic yards, and at 111.1 lb per cu ft 0.67 tons. Edging: 4 × 12 = 48 ft.

Metric: a patio of 4 × 3 m is 12 m². Block pavers of 200 × 100 mm with 3 mm joints take up 0.203 × 0.103 = 0.0209 m² each: 12 ÷ 0.0209 = 573.9, with 10 percent extra 631.3, so 632 pavers. Base 100 mm over 4.3 × 3.3 = 14.19 m²: 1.419 m³, with 25 percent extra 1.77 m³, shown as 1.78 m³, and at 1756 kg/m³ 3.12 t. Sand 30 mm: 12 × 0.03 = 0.36 m³, 0.65 t. Edging 14 m.

Around a fire pit: paving with an outer diameter of 12 ft around a 4 ft pit covers 3.14159 × (6² − 2²) = 100.5 sq ft, which takes 502 of the same pavers with 10 percent extra, and 37.7 ft of edging on the outside.

Pavers for common patio sizes

The tables use the calculator with its examples: 10 percent extra, a compacted base reaching 150 mm or 6 in past the edges with 25 percent extra for compaction, and bedding sand 30 mm or 1 in thick. Round up to whole pallets or bags as you buy them.

Base, sand and joints: what the makers say

In the United States, the Concrete Masonry & Hardscapes Association (CMHA, which took over the guidance of the Interlocking Concrete Pavement Institute) gives a minimum compacted base of 4 in (100 mm) for patios and walkways on well-drained soil and 6 in (150 mm) for residential driveways, with thicker bases on wet or weak soils and in cold climates. It specifies bedding sand of concrete sand, screeded to about 1 in (25 mm) before the pavers are compacted, and joints of 1/16 to 3/16 in (2 to 5 mm). Belgard and Pavestone give 4 to 8 in of base.

In the United Kingdom, Marshalls says at least 100 mm of MOT Type 1 sub-base for block paving and a 50 mm laying course of sharp sand; Tobermore, summarising BS 7533, gives 150 mm of sub-base and a 30 mm compacted laying course for patios and domestic driveways. In Australia, Austral Masonry describes 100 mm of compacted road base and 30 mm of washed river sand. Use the thicknesses your paver maker or local practice gives.

The base weight preset is the value that the Washington State Department of Transportation uses for crushed base course as delivered, 2,950 lb per cubic yard (1,756 kg/m³); compacted it weighs 3,700 lb per cubic yard, so a cubic yard of compacted base needs about 1.25 cubic yards as delivered. That is where the 25 percent compaction allowance comes from; the aggregate supplier Stoneco similarly says compaction can reduce volume by as much as 20 percent. The sand preset of 1.5 tons per cubic yard (1,780 kg/m³) is what the Ohio aggregate producer Kokosing uses for sands. Your supplier's figures may differ.

Edge restraints hold the pavers in place. CMHA calls them a key part of an interlocking pavement, and Tobermore's summary of BS 7533 says every paved area needs them around its perimeter; they stand on the base, which is why the base reaches past the paving. Belgard advises digging at least 6 in beyond the perimeter.

Allowance for cuts

Marshalls advises adding 10 percent to the area for block paving. That is the preset for patterns whose lines run parallel to the edges: running bond, stack bond, basket weave and 90° herringbone.

A 45° herringbone or any pattern laid at an angle needs a cut paver along every edge. We did not find a paver manufacturer or association that publishes a figure for this, so the 15 percent preset for angled patterns is this site's starting value, not a published rule. A small patio, a circle or many curves raise the share of cut pavers; so do joints wider than about 3/8 in at the edges, which CMHA says should be filled with cut pieces.

Common mistakes

• Using the nominal size of the paver. A 4 × 8 in Holland paver is smaller than 4 × 8 in; with the joint it comes close to 4 × 8 again, which is why makers count 4.5 to 4.7 pavers per square foot.
• Ordering the base by the compacted volume. Crushed stone is delivered loose and compacts, so you need more than the finished layer.
• Ordering only the area of the patio in base material. The base should reach past the edges so that the edge restraint stands on it.
• Using stone dust or masonry sand for the bedding layer. CMHA specifies concrete sand to ASTM C33.
• Forgetting the joint sand. It is bought separately after the pavers are laid; the bag states the coverage.
• Counting cut pavers as waste for a round patio. Circle kits are sold for the area of the circle; if you cut your own circle from rectangular pavers, use a higher allowance.