What this calculator works out
A block paving job comes down to five separate orders that all trace back to the same footprint: the blocks themselves, the edging that holds them in, the MOT Type 1 stone underneath that carries the load, the sharp sand they're bedded on, and the kiln-dried sand that locks the joints once they're down. This tool takes a driveway or patio's size, a block, a laying pattern and two sub-base choices, and turns all five into a shopping list at once, in tonnes, bulk bags and 25kg bags where each material is actually sold.
It works for a UK driveway in 200 × 100mm standard block or a larger 240 × 160mm format, or a US path or patio in the standard 4 × 8in clay or concrete paver, with every measurement carrying its own metric or imperial toggle so a length in metres and a depth in millimetres can sit side by side without converting by hand.
How the maths works
Area comes first, either from a rectangle's length times width or typed straight in for an odd-shaped space. A wastage percentage, set by the laying pattern, then turns that net area into the area to actually order, and dividing by the chosen block's own footprint (0.02 m² for the 200 × 100mm UK standard, for example) and rounding up gives the block count, since no supplier sells part of a block.
Edging works the same way but along a line rather than across an area. Blocks stood on end as a soldier course are spaced along the perimeter by their own width, so the edging count is simply the perimeter divided by that width, rounded up.
The sub-base and sand layers turn the same net area into a volume, then a weight, exactly the way this site's Gravel Calculator handles aggregate: area times depth gives volume, and volume times a typical density gives the tonnes to order.
Kiln-dried jointing sand is the one material measured directly in kilograms per square metre rather than by volume, since it's brushed into narrow joints rather than spread as a layer, so its rate is multiplied straight against the net area and rounded up into 25kg bags.
A worked example
Take an 8m by 5m UK driveway, 40 square metres, laid in 200 × 100mm standard block in a 45° herringbone pattern with a 150mm MOT Type 1 sub-base. Herringbone's 10% wastage allowance takes 40 m² up to 44 m² to order; at 50 blocks per square metre, that's 2,200 blocks. The full 26m perimeter, edged as a soldier course at 10 blocks per running metre for this block's 100mm width, adds 260 edging blocks. The 150mm sub-base is 40 × 0.15 = 6 cubic metres of MOT Type 1, which at roughly 2.2 tonnes per cubic metre compacted comes to about 13.2 tonnes. The 50mm sharp sand bed is 40 × 0.05 = 2 cubic metres, at 1.6 tonnes per cubic metre that's 3.2 tonnes. Kiln-dried jointing sand at this block's own default rate of about 4.0 kg per square metre needs 160kg, which rounds up to seven 25kg bags. At a rough £32 per square metre for the blocks alone, on the 44 m² ordered, that's £1,408 before sub-base, sand or labour.
The US aside: a 300 sq ft path in the standard 4 × 8in brick paver, laid stretcher bond with a lighter 5% wastage allowance, needs 315 sq ft to order; at 4.5 pavers per square foot, that's about 1,418 pavers, before the same sub-base and bedding-sand maths applies underneath.
Herringbone against stretcher and basketweave
Pattern choice is mostly a structural decision on a driveway, not just a look. A 45° herringbone pattern interlocks every block with its neighbours in two directions, which resists the twisting, scrubbing force a turning car wheel puts through a surface far better than a straight stretcher bond, where every joint line runs the same way and can work loose under repeated lateral load. That's why herringbone is the pattern most commonly recommended for driveways specifically, while stretcher bond and basketweave, which need far fewer awkward cuts at a rectangular boundary, remain entirely fine choices for patios and paths that only carry foot traffic.
The trade-off is wastage: herringbone's diagonal run means almost every boundary block needs an angled cut, and offcuts from one triangular cut rarely fit cleanly into the next gap, which is why this calculator allows 10% for herringbone against 5% for stretcher or basketweave, where most cuts are simple straight trims an installer can often reuse elsewhere on the same job.
Sub-base, bedding sand and depth choices
MOT Type 1, a graded crushed stone with no single top size, is the standard structural sub-base for flexible block paving: it compacts into a dense layer that spreads a vehicle's weight over the ground beneath rather than letting the blocks carry the load directly. A patio or footpath that only takes foot traffic typically needs around 100mm compacted; a driveway needs more, typically 150mm, and soft or clay ground is worth taking to 200mm even under a patio, since a thin sub-base on poor ground is a common reason a paved area ruts or sinks later. MOT Type 1 is ordered at its compacted density, taken here as around 2.2 tonnes per cubic metre; its loose, as-delivered density is lower, closer to 1.5–1.6 tonnes per cubic metre, which is why it needs proper compaction in thin layers rather than one deep tipped lift.
The sharp sand bedding layer sits on top of the compacted sub-base and is what the blocks are laid onto and levelled against. It's screeded to about 50mm before laying, then settles to a slimmer 25–40mm once the blocks are placed and run over with a vibrating plate compactor. This calculator orders sand at the fuller, applied 50mm figure, since that's the volume actually bought and spread, not the thinner result left once the blocks have settled in.
Edging and restraint
Flexible block paving is really a large number of loose interlocking units held in place by friction and by whatever restrains their outer edges. Without a firm edge, the outermost blocks gradually creep outward under traffic and the surface can loosen from the border inward. A soldier course, a row of blocks stood on end around the perimeter and usually bedded onto a concrete haunching, is the traditional restraint; proprietary plastic or metal edge restraints, pinned into the sub-base, are a common lighter-weight alternative. Every open edge needs a restraint of some kind; the only edges that don't are ones already held by something solid, such as a house wall, an existing kerb or a step.
Permeable paving and drainage rules
In much of the UK, paving a front garden with an impermeable block system and no provision for surface water needs planning permission once the area passes a set threshold (currently 5 square metres in England), because rainwater that would once have soaked into a lawn instead runs straight off into the drains. A permeable system, which lets water drain down through open joints and a permeable sub-base, is usually exempt from that requirement and is the more sustainable urban drainage (SUDS) choice regardless of the legal threshold, since it keeps rainwater recharging the ground rather than overloading storm drains. This calculator works out block and joint-sand quantities either way; a genuinely permeable build additionally needs a specific open-graded sub-base and jointing aggregate rather than kiln-dried sand, worth checking against current local planning rules and a permeable product's own installation guide before ordering.
Questions people ask
Why does herringbone use more blocks than stretcher bond?
It doesn't use more blocks for the same net area, but it wastes more of what's ordered: the 45° diagonal run needs a cut at almost every boundary block, and those offcuts rarely reuse cleanly elsewhere, so herringbone carries a 10% wastage allowance here against 5% for a straight stretcher or basketweave pattern.
How many block paving bricks do I need per square metre?
It depends on the block: the UK standard 200 × 100mm block is exactly 50 per square metre, a 240 × 160mm large-format block is about 26 per square metre, and the standard US 4 × 8in paver is 4.5 per square foot. Wastage is added on top to give the number actually needed to order.
Do I need edging restraints around block paving?
Yes, along every open edge. Flexible block paving is held together by friction between interlocking units, and without a firm restraint, usually a soldier course of blocks or a proprietary edge restraint, the outer blocks gradually creep and the whole area can loosen from the border inward. A wall, existing kerb or step can stand in for a restraint on that particular edge.
How deep should the MOT Type 1 sub-base be?
Around 100mm compacted for a patio or footpath that only takes foot traffic, and around 150mm for a driveway that takes a car's weight, both fairly standard domestic figures. Go deeper, up to around 200mm, on soft or clay ground even under a pedestrian area, since a thin sub-base on poor ground is a common cause of later sinking or rutting.
How much kiln-dried sand do I need for the joints?
Roughly 4kg per square metre for a new-laid UK 200 × 100mm block, within the 3.3–4.5 kg/m² range typically quoted for that size, though smaller blocks with more joint length per square metre need proportionally more. This calculator scales its default by block size and leaves the figure editable, since joint width and depth move the real number a little.
Do I need permeable paving for a driveway?
In much of the UK, paving over a front garden with an impermeable surface and no drainage provision needs planning permission once the area passes a set threshold (5 square metres in England); a permeable system that lets water drain through the joints and sub-base is usually exempt and is the more sustainable drainage choice either way. Check current local planning rules and a permeable product's own installation guide before ordering, since it needs a different open-graded sub-base and jointing material rather than kiln-dried sand.
This calculator uses verified block dimensions from published manufacturer data (Marshalls, Brett) and standard sub-base, bedding and jointing depths from published installation guides. Real coverage and material use vary with ground conditions, joint width, cutting waste and supplier-specific pack sizes, so treat the figures here as a solid ordering estimate and confirm against your own supplier's data sheet before a large order.