Calculator
Block calculator: concrete blocks and mortar
Standard 440 × 215 mm blocks lay at 10 per square metre; multiply the wall area by 10, add about 5 percent, and allow roughly 0.008 to 0.01 m³ of mortar per square metre of 100 mm blockwork.
Enter your sizes, see the materials and a diagram, then send the list for a delivered price.
Quantities are estimates using standard UK rules of thumb and are shown with their working. We check them against your job before we price anything.
How the calculation works
- Wall area = length × height, minus openings
- Blocks = area × 10, + 5% waste
- Mortar ≈ 0.0085 m³ per m² at 100 mm, scaled for thicker blocks
- Dry materials ≈ mortar × 1.33, split by your mix
Worked example
A garage wall 6 m long and 2.4 m high: 14.4 m² × 10 = 144 blocks, plus 5% = 152. Mortar about 0.12 m³: roughly 0.2 tonnes of building sand and 2 bags of cement at 1:4.
What to order with it
- Concrete & Aircrete Blocks: Dense, lightweight and aircrete blocks for walls and foundations.
- Building & Sharp Sand: Soft building sand, sharp sand and plastering sand.
- Cement: 25 kg bags of general-purpose and rapid-set cement.
Quantities are estimates. Pack sizes, bag weights and coverage vary by manufacturer; we confirm them on your quote.
Questions
How many blocks per square metre?
Standard 440 × 215 mm blocks with 10 mm joints lay at about 10 blocks per square metre of wall. Add around 5 percent for cuts.
What is the difference between building sand and sharp sand?
Building (soft) sand is fine and makes smooth mortar for laying bricks. Sharp sand is coarser, drains better and is used in concrete, screeds and paving beds.
Send your list, get a delivered price
Tell us what you need and where it is going. We check the quantities and come back with a delivered price before you commit.