Bricks, screed, render and fencing may belong to one project, but they use different physical quantities. Bricks start from wall area, screed from volume, render from area and consumption, and fencing from length and intervals.
1. Bricks: start from net wall area
An 8 m × 2.5 m wall is 20 m². A 1.20 m × 2.10 m opening is 2.52 m², leaving 17.48 m².
At an assumed 50 bricks/m²:
17.48 × 50 = 874 bricks
With 5% allowance, that becomes 917.7, so at least 918 units before packaging. The brick calculator automates the sequence. For concrete blocks, use the dedicated block calculator.
2. Screed: area becomes volume
For a 7 m × 4 m room, area is 28 m². At 5 cm = 0.05 m thickness:
28 × 0.05 = 1.40 m³
The screed calculator makes the unit conversion explicit. Average thickness matters: over 60 m², increasing from 5 to 5.5 cm changes volume from 3.00 to 3.30 m³.
3. Render: area × consumption
For 40 m² at an assumed 1.5 kg/m²:
40 × 1.5 = 60 kg
With 10% allowance: 66 kg. In 25 kg bags, 66 ÷ 25 = 2.64, so 3 bags are required.
Use the render calculator, but enter the consumption of the actual product because render consumption depends on product, layer thickness and substrate.
4. Fence: count intervals before posts
For a 20 m straight fence with a maximum 2.5 m spacing:
20 ÷ 2.5 = 8 intervals
A simple open line with eight intervals generally has nine post positions before accounting for gates, corners or special posts. If the length is 21 m, 21 ÷ 2.5 = 8.4, so eight intervals would exceed the chosen spacing and nine are needed.
The fence calculator helps explore this rounding effect.
Four methods side by side
| Work |
Starting measure |
Intermediate rule |
Purchasing result |
| Bricks |
wall m² |
bricks/m² |
units/pallets |
| Screed |
m² + thickness |
m³ |
volume/material |
| Render |
m² |
kg/m² |
kg/bags |
| Fence |
length |
intervals |
posts/panels |
Do not use the same allowance everywhere
Brick losses, render consumption uncertainty, screed thickness variation and fence geometry are different risks. When uncertainty comes from a measurement, comparing a low and high scenario can be more informative than adding an arbitrary percentage.
For 50 m² of screed, 5 cm gives 2.50 m³ while 6 cm gives 3.00 m³: a 0.50 m³ difference.
Keep the assumptions with each result—dimensions, openings, thickness or consumption, allowance and packaging—so the calculation remains understandable if the product or measurement changes.
For a reusable method across the whole project, see planning the right material quantities.
