How many bricks do I need per m² of wall? Calculation with mortar included

"How many bricks do we need for this partition?" is one of the first questions to answer before quoting any masonry job, and calculating it by eye is the quickest way to run short halfway through the day.

How much each piece covers

• Standard facing brick (24×11.5×7 cm) with a 1 cm mortar joint: covers 0.018 m² of wall each.
• Concrete block (20×20×40 cm): covers 0.08 m² each, so far fewer pieces are needed for the same area, although each weighs and costs more.

To go from area to number of pieces: divide the m² of wall by the piece's coverage (0.018 or 0.08) and add a 5% margin for breakage in transport and laying.

Worked example

For a 12 m² facing-brick partition:

1. Area: 12 m²
2. Pieces without margin: 12 ÷ 0.018 ≈ 667 bricks
3. With the 5% breakage margin already applied: 701 bricks

This is the same calculation the PresupuestoYa calculator applies automatically for the Bricklayer trade, with the line-by-line breakdown ready for the quote.

How much mortar that same wall needs

Masonry mortar for bedding bricks or blocks covers roughly 1 bag of 25 kg per 1–1.2 m² of masonry, with a standard 1–1.5 cm joint. Thicker joints use considerably more mortar without adding strength, so it doesn't pay to go over on thickness.

The usual mortar mix is 1 part cement to 3 parts sand (by volume): for each 25 kg bag of cement about 75 kg of sand is needed. Use river sand for interior mortars and crushed sand for exteriors, where more strength is needed.

After building the masonry: coverings

Once the masonry is up, the covering uses material separately:

• Cement render (exterior or damp areas): 1 bag of 25 kg per 2–2.5 m² at 1 cm thickness. Always use cement with water-repellent additives outdoors.
• Gypsum plaster (base coat and skim) (interior): 1 bag of 25 kg per 3–3.5 m² at 1.5 cm. Not suitable for bathrooms or kitchens — there you need cement mortar or an anti-damp covering.
• One-coat facade render: 1 bag of 25 kg per 1.5–1.7 m², with colour and finish built into the mix itself.

Frequently asked questions

How many bricks are there in 1 m² of wall? About 56 standard facing bricks without waste (1 ÷ 0.018), or 59 adding the usual 5% for breakage.

Is calculating concrete blocks the same as bricks? No: a concrete block covers 0.08 m² compared with the 0.018 m² of a brick, so far fewer units are needed for the same wall, although the price and weight per piece are also higher.

How long should I wait before walking on fresh mortar? At least 24 hours before walking on it, and complete setting can take up to 28 days in normal conditions.

Conclusion

Calculating pieces and mortar together —not separately or by eye— is what avoids a second trip to the merchant halfway through the job or buying too much "just in case". Automating it with the waste breakdown included gives a tight masonry quote that is easy to justify to the client.