Free UK trade calculator
Work out block paving quantities
Enter your measured area and chosen block size to get a theoretical block count, a buy quantity with your own allowance, and sub-base/bedding sand volumes. This is a quantity and planning calculator, not a site-specific pavement design, checked against current manufacturer guidance 2 October 2026.
Block count, sub-base and bedding sand calculator
This returns a theoretical block count, a buy quantity after your own waste allowance, and the sub-base and bedding sand volumes for the depths you enter. Evidence/checked date: 2 October 2026. The actual project specification, the paving product's installation guide and ground conditions on your site govern the final layer depths, construction method and product coverage. This calculator does not replace any of those.
Planning result
825
Blocks to buy, including your 10% allowance
- Measured area
- 15 m²
- Block face area
- 0.02 m²
- Theoretical blocks (before allowance)
- 750
- Sub-base volume
- 1.5 m³
- Bedding sand volume
- 0.45 m³
Method
area = length × width. Block face area = block length × block width (converted mm→m). Theoretical blocks = area ÷ block face area, shown to 2 decimal places since a whole number of blocks is not usually exact. Blocks to buy = theoretical blocks × (1 + your allowance), rounded up to a whole block only at that final step. Layer volume = area × depth. This is transparent geometric planning arithmetic, not a site-specific pavement design, a structural adequacy claim, or a manufacturer product coverage figure.
Before you order
This block count is a geometric planning estimate from the measurements above, not the manufacturer's own coverage figure. Where the product you are buying states blocks per m², a nominal module size, or a pack/pattern coverage figure, use that manufacturer figure for your final order. It accounts for the specific product, jointing gap and any mixed-size laying pattern that this calculator cannot know.
The arithmetic, shown in full
Measured area
length (m) × width (m)
Block face area
block length (mm → m) × block width (mm → m)
Theoretical blocks
measured area ÷ block face area
Blocks to buy
theoretical blocks × (1 + your allowance), rounded up to a whole block
Sub-base volume
measured area × sub-base depth (mm → m)
Bedding sand volume
measured area × bedding sand depth (mm → m)
Worked example: a 5m × 3m area is 15m². With 200mm × 100mm blocks, the block face area is 0.02m², giving 750 theoretical blocks before any allowance. A 10% allowance then rounds up to 825 blocks to buy. The theoretical figure is rarely a whole number for other measurements. This calculator shows it to two decimal places rather than rounding early, and rounds up only once, at the final buy-quantity step.
This geometric count is a planning estimate, not the manufacturer's own coverage figure. Where the product you are buying states its own blocks per m², nominal module size, or pack/pattern coverage, use that figure for your final order. It accounts for the specific product, jointing gap and any mixed-size laying pattern that a simple area ÷ block-face-area sum cannot know.
Why the depth fields are editable, not fixed
Current manufacturer guidance does not agree on a single bedding sand depth, which is exactly why this calculator leaves the depth fields open for you to set. Marshalls' block paving guide specifies a sub-base at least 100mm deep, followed by a 50mm layer of damp sharp sand for the bedding course. Tobermore's professional FAQ instead says block paving is generally bedded on about 30mm of compacted sharp sand, with the full laying-course and jointing specification in BS 7533-102:2025, and its separate sub-base guidance says depth and material depend on the traffic category and surface-course type, not a fixed figure. Neither figure is universally correct: follow the installation guidance for the specific paving system and product you have chosen, since that specification, not this calculator, governs the final depth. Permeable paving is a different system with its own sub-base design and is out of scope for this calculator.
Evidence & sources
Marshalls' current block paving guide specifies a sub-base at least 100mm in depth, followed by a 50mm layer of damp sharp sand for the bedding/laying course.
Marshalls · checked · vendor/commercial source
Tobermore's professional FAQ says concrete block paving is generally installed unbound on a bed of about 30mm sharp sand, jointed with kiln-dried sand, with full laying-course and jointing detail set out in BS 7533-102:2025.
Tobermore · checked · vendor/commercial source
Sub-base depth and material depend on the traffic category of the paved area and the surface-course type being used, not on a single fixed figure, and permeable paving is a separate system with its own sub-base design.
Tobermore · checked · vendor/commercial source
Prices and terms change. If a source above no longer matches what we've written, tell us via the corrections page and we'll fix it.
Questions trades ask about block paving quantities
How many block pavers do I need for my area?
Divide your measured area by the face area of one block (block length × block width, converted to metres) to get a theoretical count, then add your own cutting and breakage allowance and round up to a whole block only at that final step. This calculator does that arithmetic from the measurements and block size you enter. It is a geometric planning estimate, so where the manufacturer states its own blocks-per-m² or pack coverage figure for the product you are buying, use that for your final order instead.
How deep should the sub-base and bedding sand be?
There is no single figure that fits every site or product, and current manufacturer guidance does not even agree on the bedding sand depth. Marshalls' own block paving guide specifies a sub-base at least 100mm deep, followed by a 50mm layer of damp sharp sand for the bedding course. Tobermore's professional FAQ says block paving is generally bedded on about 30mm of compacted sharp sand instead, with the full specification set out in BS 7533-102:2025, and its separate sub-base guidance says depth also depends on traffic category and surface-course type. That is why this calculator's depth fields are editable rather than fixed. Enter the depths from the specific product and project specification you are actually using, not a single number taken from either manufacturer.
Can this calculator tell me how many tonnes or bulk bags of sub-base I need?
Only if you enter a density yourself. TBV does not publish a generic aggregate density, bulk-bag coverage figure or jointing-sand coverage rate, because these vary by supplier and product. Enter the density from your own supplier's product data if you want a tonnage; otherwise the calculator shows volume in cubic metres only.
Is this the same as a driveway construction design?
No. This tool answers one question: how many blocks and how much sub-base/sand volume a measured area needs at the depths you choose. It does not assess ground conditions, drainage, falls, edge restraint, loading, permeable-paving design or any other part of a site-specific pavement specification.