Blockwork Calculator UK | How Many Blocks Do I Need?
Free UK blockwork calculator. Enter wall dimensions to get the number of concrete blocks, mortar volume and wall area. Based on standard 440×215mm UK blocks.
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Results are estimates only and may vary depending on site conditions, material specifications and waste. EasyEstimate and its affiliates accept no responsibility for any loss or damage arising from reliance on these figures. Always verify quantities with your supplier before ordering.
How to Calculate Blocks for a Wall
Concrete blockwork is faster and cheaper to lay than brickwork for most structural and inner-leaf applications. The calculation is straightforward: work out the wall area, then divide by the face area of one block (including mortar joints).
The Formula
For standard UK concrete blocks (440×215mm, 10mm joints):
- Co-ordinating face size = 450mm × 225mm = 0.1013 m²
- Blocks per m² = 1 ÷ 0.1013 ≈ 10 blocks per m²
- Wall area = Length (m) × Height (m)
- Blocks needed = Wall area × 10 × (1 + waste%)
UK Standard Concrete Block Dimensions
| Measurement | Size |
|---|---|
| Block length | 440 mm |
| Block height | 215 mm |
| Mortar joint | 10 mm |
| Co-ordinating face | 450 × 225 mm |
| Blocks per m² | ~10 |
| Common thicknesses | 100 mm, 140 mm, 215 mm |
Worked Example
Wall: 5m long × 2.4m high, 5% waste
- Wall area = 5 × 2.4 = 12 m²
- Blocks required = 12 × 10 = 120 blocks
- Add 5% waste = 120 × 1.05 = 126 blocks
- Mortar = 12 × 0.012 = 0.14 m³
Block Coursing and Storey Heights
Each course of standard blockwork is 225mm tall (215mm block + 10mm mortar). This co-ordinates with three courses of standard brickwork (3 × 75mm = 225mm), making brick and block cavity walls easy to detail.
| Courses | Wall height |
|---|---|
| 5 | 1.125 m |
| 8 | 1.800 m |
| 10 | 2.250 m |
| 11 | 2.475 m |
Dense vs Lightweight Blocks
Dense aggregate blocks (e.g. Lignacite, Forticrete):
- High compressive strength (7–20 N/mm²)
- Suitable for loadbearing walls, below DPC, retaining walls
- Heavier (up to 22kg per block)
Lightweight aerated blocks (e.g. Thermalite, Celcon):
- Easier to cut and handle
- Better thermal insulation
- Common for inner leaf of cavity walls
- 600–900 kg/m³ density
Beyond Block Quantities
This calculator gives you blocks, mortar and wall area. A complete blockwork estimate also includes:
- Wall ties (cavity walls, typically at 600mm horizontal and 450mm vertical spacing)
- DPC (at base of wall and over lintels)
- Lintels (over openings)
- Insulation (cavity batt or rigid board for inner leaf)
- Labour (an experienced blocklayer typically lays 80–120 blocks per day)
EasyEstimate’s full blockwork calculator includes all these items with current UK pricing, ready to export as a professional material schedule or client estimate.
Related Calculators
- Brick Calculator — calculate bricks, mortar and wall area for the outer leaf or facing brickwork
- Concrete Calculator — calculate concrete volume and bags for foundations and slabs
Frequently Asked Questions
- How many concrete blocks per square metre?
- Standard UK concrete blocks (440×215mm face, with 10mm mortar joints giving a 450×225mm co-ordinating size) produce approximately 10 blocks per square metre of wall face.
- What are the standard UK concrete block sizes?
- The most common UK concrete block is 440mm long × 215mm high × 100mm thick (co-ordinating size 450×225mm including mortar joints). Blocks are also available in 140mm and 215mm thicknesses for loadbearing and insulating applications.
- How much mortar for blockwork?
- Allow approximately 0.012 m³ of mortar per m² of blockwork. This is less than brickwork because blocks are larger. A typical mix is 1:6 (cement:sand) for general blockwork, or 1:4 for below-DPC or engineering applications.
- What is the difference between dense and lightweight blocks?
- Dense aggregate blocks (typically 1,350–2,000 kg/m³) are strong, loadbearing and suit below-ground or structural applications. Lightweight aerated blocks (Aircrete, e.g. Thermalite, Celcon) at 600–900 kg/m³ are easier to cut, have better thermal performance, and are commonly used for inner leaf cavity walling.
- How many courses of blocks in a standard storey height?
- A standard storey height of 2.4m requires approximately 10–11 courses of blockwork (225mm co-ordinating height per course including mortar joint). Block and brick coursing is designed to align every three brick courses to one block course (3 × 75mm = 225mm).
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