Block paving calculator: blocks and sand
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| Paved area | rectangle 5 m × 4 m |
| Block length | 200 mm |
| Block width | 100 mm |
| Pattern | Stretcher bond |
| Waste allowance | 5% |
| Kiln-dried sand bag size | 25 kg |
| Waste allowance | 5% |
| Sharp sand density | 1.6 t/m³ |
| Bulk bag size | 0.85 t |
Order: 1,050 blocks
| Result | Value |
|---|---|
| Blocks | 1,050 |
| Blocks per m² (no waste) | 50 |
| Paved area | 20 m² |
Show the working
- Blocks per m²: 1 ÷ (0.2 × 0.1 m) = 50
- Blocks: 20 m² × 50 × 1.05 (5% waste) = 1,050, rounded up = 1050
How it works
- Blocks per m² = 1 ÷ (block length × block width), in metres. Block paving joints are nominal (the blocks have spacer nibs), so no joint is added
- Blocks = area × blocks per m² × (1 + waste), rounded up
- Laying course sharp sand (t) = area × depth × sand density × (1 + sand waste)
- Kiln-dried sand (kg) = area × kg per m²; bags rounded up
- Edging pieces = edge length ÷ piece length, rounded up
Herringbone needs more cutting at the edges than stretcher bond, so allow more waste.
Lay to the block maker's guide and BS 7533; driveways need a deeper sub-base than paths.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Block length | 200 mm | Common UK size Not yet checked against the source | From your product brief v2 L2 (200 × 100 default block). Check the product. |
| Block width | 100 mm | Common UK size Not yet checked against the source | From your product brief v2 L2 (200 × 100 default block). Check the product. |
| Waste allowance: Stretcher bond | 5 % | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 L1 PA1 and L2 BP1 (5%). Researcher to check against a laying guide. |
| Waste allowance: Herringbone | Enter from the bag, pack or tin | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 L2: pattern waste for herringbone. Researcher to source from a block maker's laying guide. |
| Laying course depth | Enter from the bag, pack or tin | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 L2: laying course depth. Researcher to source (BS 7533 / block maker's guide). |
| Kiln-dried sand | Enter from the bag, pack or tin | Typical value Not yet checked against the source | From your product brief v2 L2: kiln-dried jointing sand rate is null in the brief; from the bag or block maker. |
| Kiln-dried sand bag size | 25 kg | Common UK size Not yet checked against the source | From your product Common small bag. |
| Waste allowance | 5 % | Our assumption Not yet checked against the source | Our choice: change it to suit your job Spreading and settling; compaction varies. |
| Sharp sand density | 1.6 t/m3 Sources range 1.6–1.7 t/m3 | Typical value Not yet checked against the source | aggregatecalculator.co.uk aggregate density table (checked 19 October 2026) Damp sand bulks; order by weight. |
| Bulk bag size | 0.85 t | Common UK size Not yet checked against the source | builder.tools bulk bag figure (checked 19 October 2026) Varies by merchant; check yours. |
Regulations and standards
- BS 7533 (pavements of flags and pavers): see the explainer for laying guidance
Explained: BS 7533 (paving).
Our checks use the guidance for England unless a badge says otherwise. Wales, Scotland and Northern Ireland have their own rules: check the source for where you live.