How to count paving slabs
Count the actual grid with joints and cutting allowance
Back to calculator ↑Draw a layout
Measure both axes and enter the actual two slab dimensions. Mixed sizes or curved edges need a separate layout.
Draw the rectangle from the true paving edges, excluding separate edging or drains. Mark posts, notches and sloped edges before relying on a simple grid. Place full and cut slabs on the drawing, especially along prominent sight lines. Choose pattern direction and a starting edge: turning rectangular slabs can change the cut schedule even when total area remains the same.
Include joints
Joint width is between slabs, not an outer border. Rows are rounded up from (area width + joint) ÷ (slab width + joint).
Enter the dimensions of one actual slab. A joint is space between adjacent slabs, not an extra margin around every outer edge. Adding one joint to both the measured span and module denominator gives the correct count when the last slab fits exactly. Check whether the supplier dimensions are actual sizes and whether the paving system permits the entered joint width.
Default example
With defaults, the 5,000 mm axis needs nine positions using a 605 mm slab-plus-joint module, while the 3,000 mm axis needs five rows. That is 45 slab positions; 10% allowance gives 49.5, rounded to 50 full slabs. If sold in packs, divide 50 by the pack count and round up once more. Edge pieces will be cut to the actual boundary.
Convert to packs
Divide the allowed slab count by slabs per pack and round up. If edge offcuts can be reused, check the drawing to reduce the order.
This is a slab count, not a base, bedding, fall, drainage or jointing estimate. A cut piece may fit another edge when its dimensions and pattern permit, but the tool does not credit such reuse automatically. Review the cut drawing and exact product before paying, particularly for directional finishes or mixed-size packs sold in fixed proportions.
Common questions
How many joints are counted?
Joints occur only between slabs, so a row of n slabs has n−1 internal joints. Account for any separate perimeter border in the measured span or a detailed layout.
Do actual slab dimensions matter?
A selling size may be nominal. A few millimetres difference in actual slab or joint size can change a row count near a boundary; verify the specification and a sample.
Is the price a full project cost?
It multiplies the rounded full packs by the entered pack price. Base, bedding, adhesive, jointing, edging and labour need separate quantities for the chosen paving system.
Sources and calculation guidance
Check these against your chosen product’s label and instructions.