Paving Calculator UK
Work out exactly how much paving you need before you order. This UK paving calculator turns your patio or driveway dimensions into a block-paver or slab count, adds your wastage allowance, and works out the bedding sand underneath — plus an optional cost estimate. It handles the standard UK block size (200 × 100 mm) and the common concrete slab sizes from 300 × 300 mm up to 600 × 600 mm, or enter a custom size. Everything is metric-first, with an imperial toggle if you're measuring in feet.
Enter a number greater than zero.
Enter a number greater than zero.
Depth affects load rating, not quantity.
Typical block-paving sand bed 30–50 mm; typical slab mortar bed 30–50 mm.
Enter your dimensions above to see your paving estimate.
How this calculator works
It takes the area (from dimensions or a direct entry), divides by the plan area of one block or slab to get the raw count, then applies your wastage allowance and rounds up. For block paving the standard 200 × 100 mm paver gives 50 blocks per square metre. It then works out the bedding sand from the area and the bed depth you enter, converts that to tonnes and bulk bags, and — for block paving — estimates the kiln-dried jointing sand to brush into the joints.
Takeaway: enter the area and the unit size and you get the order quantity with waste already built in — no separate sum needed.
Formulas used
- Area = length × width
- Slabs = ⌈(area ÷ slab area) × (1 + waste %)⌉
- Blocks = ⌈area × blocks per m² × (1 + waste %)⌉, where blocks per m² = 1,000,000 ÷ (block L × block W in mm)
- Bedding sand = area × bed depth; tonnes = volume × 1.6; bulk bags = ⌈tonnes ÷ 0.85⌉
- Jointing sand (block paving) ≈ 1 × 25 kg bag per 11 m²
Takeaway: the unit count is driven by the size of the paver, and the sand by the bed depth — get those two right and the rest follows.
UK paving size reference
| Unit | Plan size | Coverage | Units per m² |
|---|---|---|---|
| Block paver (standard) | 200 × 100 mm | 0.02 m² | 50 |
| Slab | 600 × 600 mm | 0.36 m² | 2.78 |
| Slab | 600 × 300 mm | 0.18 m² | 5.56 |
| Slab | 450 × 450 mm | 0.2025 m² | 4.94 |
| Slab | 400 × 400 mm | 0.16 m² | 6.25 |
| Slab | 300 × 300 mm | 0.09 m² | 11.11 |
Takeaway: a standard block driveway needs 50 blocks per m²; a 600 × 600 slab patio needs under three slabs per m².
Worked example — block paving driveway
A driveway measuring 6 m × 4 m = 24 m², laid in 200 × 100 mm blocks in a 45° herringbone pattern (so 15% wastage), on a 50 mm sharp sand laying course.
- Blocks per m² = 50, so raw blocks = 24 × 50 = 1,200
- With 15% wastage: 1,200 × 1.15 = 1,380 → 1,380 blocks
- Bedding sand = 24 × 0.05 = 1.2 m³ → 1.2 × 1.6 = 1.92 t → 3 bulk bags (850 kg)
- Jointing sand = 24 ÷ 11 ≈ 3 × 25 kg bags
Takeaway: on a herringbone drive the 15% waste matters — that's the difference between ordering 1,200 blocks and being 180 short with cuts around every edge.
Worked example — slab patio
A patio measuring 5 m × 4 m = 20 m², in 600 × 600 mm slabs (0.36 m²), 10% wastage, on a 40 mm mortar bed.
- Raw slabs = 20 ÷ 0.36 = 55.6
- With 10% wastage: 55.6 × 1.10 = 61.1 → 62 slabs
- Bedding sand = 20 × 0.04 = 0.8 m³ → 0.8 × 1.6 = 1.28 t → 2 bulk bags
Takeaway: for a full-mortar-bed patio, work out the sand from the bed depth, then mix it roughly 4:1 with cement — the mortar calculator handles the cement side.
How much wastage to allow
The laying pattern matters more than the paver: stack-bond or straight-coursed full slabs with clean edges can be under 5%; standard bonds around 10%; 45° herringbone block paving with lots of cut edges runs 12–15%. Also flag that concrete paving colour varies between production batches, so ordering from a single batch matters as much as the count.
Takeaway: pick the wastage figure from your pattern, not a blanket 10% — herringbone and lots of curves need more.
Don't forget the sub-base and edging
This tool covers the pavers and the sand laying/bedding course, not the compacted sub-base (Type 1 MOT) underneath or the edge restraints. For the sub-base quantity, the gravel & sub-base calculator does the Type 1 layer.
Takeaway: budget separately for the Type 1 sub-base and edging — they're not in the paver count but they decide whether the paving lasts.
UK standards and a note on planning
BS 7533 is the British Standard series for pavements of concrete blocks, clay pavers and natural stone (BS 7533-101 covers bound construction, BS 7533-102 unbound/sand-laid). Since the 2008 changes to permitted development, a new or replacement front driveway over 5 m² that drains to a hard impermeable surface needs planning permission unless it's permeable or drains to a permeable area.
Takeaway: lay to BS 7533 and, on a front driveway, keep it permeable or drained to a border to stay inside permitted development.
Frequently asked questions
Related tools
- Gravel Calculator UK — loose gravel volume, tonnes and bulk bags
- Gravel & Sub-Base Calculator — Type 1 MOT sub-base under paving and slabs
- Driveway Cost Calculator UK — full installed cost for block paving, gravel and more
- Mortar Calculator — sand and cement for the bedding mortar
Guides worth reading
- How Many Paving Slabs Do I Need? UK Guide — slabs and blocks per m², wastage and pricing worked through
Disclaimer: This calculator is for planning and estimating only. Actual quantities vary with paver size, laying pattern, cutting layout, bed depth, sub-base and site conditions. Always confirm final quantities and order from a single batch before buying.