Concrete Block Calculator
Find how many concrete blocks you need for a wall, and the sand and cement to lay them.
Measure your job
Your answer
For a 10 m² wall (100 mm blocks). Mortar: 1 bag of cement, plus building sand, mixed 1 : 5.
Bulk bags are 800 kg. Bags are rounded up.
This answer is a guide. For footings, walls or anything that holds weight, check your local building rules or ask a builder or engineer.
What it costs
UK middle prices from October 2026, with VAT. Cement: £8.39 a 25 kg bag (7 prices from 3 sellers). Bulk bags: £75, building sand £67.35 (3 sellers each). Few prices, so treat them as a rough guide. Blocks: £2.40 each, the middle of only 3 sellers (a Wickes sale price).
Quick answers
- Blocks per m²
- 9.88, or about 10, blocks of 440 × 215 mm, with 10 mm joints.
- A 5 × 2 m wall
- 99 blocks. You would buy 2 pallets of 72, or 1 pallet and 27 loose.
- Blocks on a pallet
- 72 dense 100 mm blocks, about 1,320 kg, for Tarmac's block at Wickes.
- Block weight
- About 18.2 kg for a 100 mm dense block. A 100 mm aircrete block is about 7–7.6 kg.
- Price
- About £2.40 each with VAT (a Wickes sale price), for a 100 mm dense block. That is the middle of only 3 sellers.
How to work it out
- Measure the length and height of the wall in metres.
- Multiply them for the area in m². Take off doors and windows.
- Multiply the m² by 9.88 for 440 × 215 mm blocks.
- Round up, then add a few for cuts and breaks.
- To count pallets of dense 100 mm blocks, divide by 72.
5 × 2 m = 10 m²
10 × 9.88 = 98.8 → 99 blocks
99 ÷ 72 = 1.38 → 2 pallets
Breeze blocks per m² for common walls
The calculator shows your block count as the big number. For a quick check, use this table.
| Wall | m² | Blocks | Pallets of 72 |
|---|---|---|---|
| 3 × 1 m | 3 | 30 | 1 |
| 5 × 1 m | 5 | 50 | 1 |
| 5 × 2 m | 10 | 99 | 2 |
| 10 × 2 m | 20 | 198 | 3 |
| 10 × 2.4 m | 24 | 238 | 4 |
440 × 215 mm blocks, 9.88 per m². No doors, windows or spares. Pallets: dense 100 mm blocks.
Kilsaran's calculator uses 9.88 blocks per m². Each block and its 10 mm joint fill 450 × 225 mm of wall. That also gives 9.88 per m², so the two agree.
Block sizes and weights
In the UK, people call these breeze blocks or concrete blocks. Makers such as H+H and Forterra make them 440 × 215 mm on the face. Only the thickness changes.
| Thickness | Aircrete (H+H) | Aircrete (Forterra) | Dense 7.3 N |
|---|---|---|---|
| 75 mm | 5 kg | 5.7 kg | – |
| 100 mm | 7 kg | 7.6 kg | 18.2 kg |
| 140 mm | 10 kg | 10.6 kg | – |
| 150 mm | 11 kg | 11.3 kg | – |
| 215 mm | 16 kg | 16.3 kg | – |
Aircrete weights at normal moisture, as laid. Dense: Tarmac's block at Wickes.
- Aircrete is the light block. Both makers rate it at 3.6 N/mm².
- Dense blocks are about 2.6 times as heavy. Tarmac's 100 mm block is 7.3 N/mm².
Which block you need depends on the job. If the wall holds weight, check your local building rules or ask a builder or engineer.
Pallets and price
Wickes sells Tarmac's 100 mm dense block in pallets of 72. A full pallet weighs about 1,320 kg. We found no maker's pallet count for aircrete blocks.
Prices for a 100 mm dense block, with VAT, from Wickes, Tippers and Lawsons:
- Lowest: £1.60
- Middle: £2.40 (a sale price at Wickes, was £2.70)
- Highest: £2.57
With only 3 sellers, treat these as a rough guide. So 99 blocks cost about £238 at the middle price.
Mortar for your blocks
Under the block count, the calculator gives the building sand and 25 kg bags of cement. It allows about 1.54 kg of sand per block. That comes from Cemex's figure of about 1 litre of mortar per block.
To use bags of mortar mix, Cemex says one 25 kg bag lays about 12 blocks. So 99 blocks take 9 bags. Our block mortar calculator has more on this.
Questions people ask
How many cement or breeze blocks per square metre?
About 9.88, says Kilsaran. That is for 440 × 215 mm blocks with 10 mm joints. So 10 m² of wall takes 99 blocks.
How many breeze blocks do I need to build a wall?
Multiply the wall's length × height in metres, then × 9.88. A 5 × 2 m wall takes 99 blocks. Take off doors and windows first.
How many cement blocks on a pallet?
Wickes sells Tarmac's 100 mm dense block 72 to a pallet. That pallet weighs about 1,320 kg. We found no maker's pallet count for aircrete blocks.
How many bricks to a breeze block?
About 6, by the area of the face. A single brick wall has about 60 bricks per m², against 9.88 blocks.
What size is a concrete block?
440 × 215 mm on the face. H+H makes them 75, 100, 140, 150 and 215 mm thick.
Should I order extra blocks?
We found no UK figure for spare blocks. Travis Perkins adds 5% for bricks. Our count has nothing spare, so add a few for cuts and breaks.
Why do US block calculators give a different count?
They count US blocks, called CMU blocks or cinder blocks, of 8 × 16 inches. That is about 12 per m². UK blocks are bigger, at 9.88 per m².
Where our numbers come from
- Blocks per m² and mortar per block: Kilsaran calculator
- Aircrete block weight: H+H Celcon Standard (100 mm = 7 kg)
- Aircrete block weight: Forterra Thermalite Shield (100 mm = 7.6 kg)
- Dense block weight: Wickes, Tarmac 7.3N 100 mm (18.2 kg)
- Block price: the middle of 3 UK sellers (Oct 2026)
- Bricks per m² and 1:5 mortar: Travis Perkins brick calculator
- Mortar per bag: Cemex (25 kg lays 12 blocks or 20 bricks)
- Block size: Concrete Masonry & Hardscapes Association (TEK 02-02B)
- Unit sizes: NIST Handbook 44, Appendix C (1 ft = 0.3048 m; 1 US gallon = 231 cubic inches)
- Mortar and render mixes, cement and mortar per tonne of sand: MPA sheet 04
- Mix ratios and 25 kg bags: Heidelberg General Purpose cement data sheet
- Ballast weight: Wickes ballast bulk bag (800 kg covers 9.7 m² at 50 mm)
- Cement price: the middle of 7 prices from 3 UK sellers (25 kg, Oct 2026)
- Bulk bag prices: the middle price from 3 UK sellers each (Wickes, Tippers, Lawsons; Oct 2026)
Made by BuildersCount. Last checked 4 Oct 2026.
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