Measure only the surface that receives units
Trace the finished pavement boundary, then split an irregular plan into rectangles, squares, triangles, circles, or surveyed segments. In the calculator, use length × width for a rectangle, one side for a square, the full edge-to-edge diameter for a circle, or base × perpendicular height for a triangle. Subtract planting openings, drains, columns, and structures only when no paver will be cut around or beneath them. Keep borders and accent bands as separate zones when they use another size, color, or orientation.
A sloping walk is normally ordered from its actual paved surface, not automatically from a horizontal projection. Confirm which dimensions the drawings report. Curves, fans, soldier courses, herringbone fields, and narrow returns can have similar areas yet create very different cutting work, so retain a marked layout rather than relying on one gross square-foot number.
Read the product schedule before calculating coverage
- Identify manufacturer, collection, shape, nominal and actual dimensions, thickness, spacer or joint provisions, and pieces per package or pallet from current product data.
- Determine whether published square-foot coverage already reflects the intended joint and whether a package contains one size or a fixed blend of several sizes.
- Verify that the unit is specified for the application. ASTM C936 covers solid concrete interlocking paving units, but purchasers must still state desired properties and confirm availability.
- Keep edge units, permeable units, slabs, clay pavers, and replacement pieces distinct when they follow another specification or coverage convention.
Use a module that agrees with the joint design
Manufacturer coverage
When the exact product publishes pieces per square foot or area per pallet for its intended installation, that declaration is usually the cleanest basis. Record the edition and package composition.
Single rectangular unit
A calculated laying module can include unit length and width plus the designed joint contribution. Along either direction, n units contain n−1 internal joints, so the directional ratio is (project dimension + one joint) ÷ (unit dimension + one joint). For example, a 16.125 by 8.125 inch rectangle exactly fits a 2-by-2 grid of 8-by-4 inch pavers with 1/8 inch internal joints: four pavers, not the smaller quotient produced by dividing bare project area by full repeated-module area.
Circle or triangle zone
The calculator uses π × (diameter ÷ 2)² for a circle and base × perpendicular height ÷ 2 for a triangle, then divides that area by the paver-plus-joint module. This is a transparent area estimate, not a directional row or perimeter cut plan; curved and angled edges need a project-specific allowance.
Multi-size or repeating pattern
Use the manufacturer's repeat or bundle ratio. Dividing total area by the smallest piece cannot preserve the required mix of shapes and may leave unusable quantities of one size.
Build a cut allowance from the layout
- Review the perimeter
Straight dimensions coordinated to the module may need few cuts. Curves, diagonals, small insets, and numerous penetrations create more offcuts and breakage risk.
- Test reuse assumptions
A cut piece can be reused only when its remaining size, finish, orientation, and edge condition suit another location. Do not count every offcut as a full replacement unit.
- State the chosen allowance
Add the designer's or installer's project factor transparently after the base unit count. CMHA's guide specification leaves many layout and cut details project-editable, so one waste percentage cannot be presented as a standard for every pattern.
- Round by packaging
Convert to whole pieces, bundles, layers, or pallets using the current supplier package. Keep spare attic stock, delivery minimums, and return restrictions on separate documented lines.
Reproduce module and package checks
- One-module identity
Enter an 8 by 4 inch project, one 8 by 4 inch paver, zero joint, zero allowance, and one piece per package. Both directional ratios are 1, so the result is one paver and one package.
- Typical patio quantity
Enter 12 by 16 ft, 6 by 9 inch pavers, zero joint, 10% allowance, and loose pieces. The base is 512 pavers; 512 × 1.10 = 563.2, so the final whole-piece order is 564.
- Internal-joint boundary
Enter a 16.125 by 8.125 inch project, 8 by 4 inch pavers, a 0.125 inch joint, zero allowance, and loose pieces. Each direction contains exactly two pavers with one internal joint, so the base and order are exactly four pieces.
- Circular patio check
Choose Circle, enter a 10 ft diameter, 6 by 9 inch pavers, zero joint, 10% allowance, and loose pieces. The area is about 78.5 ft², the base is about 209.44 paver modules, and the final whole-piece order is 231 after the declared allowance.
Estimate the pavement assembly as independent materials
CMHA describes interlocking concrete pavement as a system that includes a prepared subgrade, aggregate base where required, a nominal bedding layer, units, joint filling, edge restraint, and compaction. Use the gravel calculator for the specified base course and the sand calculator for bedding or joint material, with distinct depths and supplier data. Verify each mapped zone first in the square footage calculator if the plan is complex.
The unit count does not design pavement thickness, drainage, slope, restraint, accessibility, frost protection, vehicle loading, or permeable-pavement storage. Confirm the current detail and local requirements with the responsible designer and installer. Preserve the area sketch, product module, pattern ratio, base count, cut allowance, package rounding, and source documents so substitutions can be recalculated rather than guessed.