How the block count is worked out
The paved area is length multiplied by width. One block covers its face size, so the area divided by the block area gives the count before waste.
A standard 200 by 100 mm block covers 0.02 square metres, which is 50 blocks per square metre. That is the trade figure, and it holds for 60 mm and 80 mm thick blocks because only the face matters.
The waste allowance covers cuts at edges, corners and around inspection covers. Five per cent is normal for a simple rectangle.
Worked example
A drive 5 metres by 3 metres is 15 square metres. At 50 blocks per square metre that is 750 blocks, and adding 5 per cent gives 788 blocks.
A path 1 metre wide and 12 metres long is 12 square metres, which is 630 blocks after the same allowance.
What the block count does not include
Block paving sits on a compacted sub-base and a 30 to 50 mm bedding layer of sharp sand. Neither is in this figure, and both are usually larger quantities than the blocks themselves in volume terms.
Edge restraints are essential. Without a concrete or plastic edge, the outer blocks spread under load however well they are laid.
Cutting at edges and around covers is where most waste comes from. A drive with several inspection covers, a curved edge or a herringbone pattern at 45 degrees needs 10 per cent rather than 5.
Limits of this calculator
It counts blocks from a nominal face size. Real blocks have a 2 to 3 mm joint, so a very large area will be a few blocks out, which the waste allowance covers.
It does not calculate sub-base, bedding sand, jointing sand, membrane or edge restraints.
It does not check the laying pattern, the fall for drainage or whether the sub-base is adequate for vehicles.
For US paver sizes and square feet, use the US block paving calculator.
Inputs for the block paving calculator
Paved length
Length of the driveway, path or patio in metres.
Paved width
Width of the same area in metres.
Block length
Long face of the block in millimetres. A standard block is 200 mm.
Block width
Short face of the block in millimetres. A standard block is 100 mm.
Waste allowance
Extra for edge cuts and covers. Five per cent for a simple rectangle.
CALCULATOR QUESTIONS
UK block paving calculator questions
How many blocks are in a square metre?
Fifty for a standard 200 by 100 mm block, which is the trade figure regardless of thickness.
How many blocks come on a pallet?
It varies, commonly around 300 to 400 for a 200 by 100 mm block. Divide the total by the pack size to see how many packs to order.
Do I need more for a curved edge?
Yes. Curves, circles and 45 degree herringbone all need more cutting, so use 10 per cent waste.
Is sand included?
No. Bedding sand and jointing sand are separate, and the bedding layer is usually 30 to 50 mm deep.