Hollow Brick Quantity Calculator
Brick count, mortar volume and bricks per m³ from wall thickness and format.
Quick answer
With the default inputs: Wall length 10 · Wall height 3 · Openings area 0 m² etc.Total bricks 2472 blocks
Edit the inputs below to recalculate.Inputs
Result
Total bricks
2472blocks
| Net wall area | 30.00m² |
| Bricks through thickness | 2blocks |
| Bricks per m² | 80.0blocks/m² |
| Bricks per m³ | 333blocks/m³ |
| Wall volume | 7.20m³ |
| Mortar volume | 1.06m³ |
| Mortar share | 14.7% |
| Mortar mass | 2013kg |
Hollow bricks have 25-35% voids that mortar does not fill, so mortar use is slightly below a solid-brick wall of the same volume. Joints run 8-12 mm, nominally 10 mm.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Net area | A = length × height − openings |
| Through thickness | k = round(thickness ÷ (brick width + joint)) |
| Per m² | n = k ÷ ((length + joint) × (height + joint)) |
| Total | N = ceil(A × n × (1 + waste)) |
| Mortar | V = wall volume − N × brick volume |
A 10 m × 3 m wall, 240 thick, 240×115×90 bricks with 10 mm joints: 2 bricks through the thickness, 80 per m², 2472 in total and about 1.24 m³ of mortar.
How to work it out
- Net wall area A = length × height − openings.
- Blocks through the thickness k = round(wall thickness ÷ (block width + joint)). A 240 wall with 115 mm blocks gives k = 2.
- Blocks per square metre n = k ÷ ((block length + joint) × (block height + joint)).
- Total N = ⌈A × n × (1 + waste)⌉, with waste normally 3%.
- Mortar = wall volume − N × block volume (net), then × 1.05-1.10 for consumption.
Where it goes wrong
- Rounding k down — 240 ÷ 125 = 1.92 rounds down to 1, halving the block count. It must be rounded to nearest.
- Treating hollow bricks as standard bricks — hollow units are 240×115×90, with 90 mm height rather than 53, so blocks per square metre differ by 40%.
- Ignoring the void ratio in weight — hollow brick is 20-30% lighter than solid, and using solid density overstates mortar and haulage.
Material and cost
Fired hollow brick runs 0.55-0.85 each by size and region, cheaper than solid and more mortar-efficient. A 240 wall takes about 80 blocks per square metre: roughly 55 per m² in material and 120-150 per m² with mortar and labour.
On site
- Orient the voids vertically to the load — laying hollow bricks on their side collapses strength.
- Wet the bricks 1-2 days ahead to 10-15% moisture; dry bricks rob the mortar of water.
- Fix ties into the solid webs, never into a void.
Basis
- GB 50203-2011 Code for acceptance of masonry construction, Chapter 5 (brick masonry)
- GB 13544-2011 Fired perforated bricks and blocks
- GB 50003-2011 Code for design of masonry structures, Chapter 3 (material strength)
FAQ
What is the difference between perforated and hollow brick?
Perforated brick has at least 25% voids in many small holes and may be used in load-bearing walls; hollow brick has at least 40% voids in large holes and is generally for non-load-bearing infill. Using the wrong one leaves a load-bearing wall non-compliant — check the marking and mill certificate, not the look of it.
Why only 40 bricks per m² in a half-brick wall?
The brick lies along the wall: a 240 mm long brick occupies 250 mm of length and a 90 mm high brick occupies 100 mm of height, so one brick covers 0.025 m² and there are exactly 40 per m². A 240 mm wall has two side by side, doubling it to 80 — that is what the through-thickness factor accounts for.
Which mortar grade should I use?
Load-bearing walls generally use M5 or M7.5 cement-lime mortar, non-load-bearing infill M5, and damp or below-ground work M7.5 or better in cement mortar. Stronger is not better: over-strong mortar deforms less and cracks at the brick interface. Follow the design specification.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Hollow Brick Quantity Calculator. 2026-10-25. https://jianzhujisuan.com/en/hollow-brick
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.