Mortar calculator
Mortar consumption is driven by the joints: a thick brick wall has far more joint volume per m² than a thin-bed aerated-concrete wall. Choose the type of masonry and the calculator gives the dry mortar and the bags.
Your measurements
Result
- Dry mortar needed
- 1,800 kg
- Bags to buy
- 72 pcs
Joints thicker than 1 cm, or perforated bricks whose holes fill with mortar, increase consumption.
How the calculation works
- Consumption per m² of wall: about 5 kg/m² of adhesive for 25 cm aerated concrete and about 45, 90 or 135 kg/m² of dry mortar for 12.5, 25 or 37.5 cm brick walls.
- Mortar (kg) = wall area × consumption per m².
- Bags = kilograms ÷ bag size, rounded up.
Worked example
For 20 m² of 25 cm brick wall: 20 × 90 = 1,800 kg of dry mortar, which is 72 bags of 25 kg. The same wall in aerated concrete with adhesive would need only about 100 kg (4 bags).
What the calculator assumes
- With solid bricks and ~1 cm joints, mortar takes about 0.23 m³ of each m³ of masonry; a litre of fresh mortar needs about 1.6 kg of dry mix.
- Aerated concrete is laid with 1–3 mm thin-bed adhesive, about 20 kg per m³ of masonry.
When to adjust the result
- Joints thicker than 1 cm, or perforated bricks whose holes fill with mortar, increase consumption.
- If you mix mortar on site from cement, lime and sand, calculate the components with the cement calculator.
Getting mortar right
Mortar should be weaker than the bricks or blocks it bonds, so cracks form in the joints rather than through the units. General masonry often uses about 1:1:6 cement:lime:sand; harder mixes are for below ground or exposed walls; soft lime mortars for old masonry.
Mix only what you can use in about an hour or two, and do not re-temper mortar that has started to set. Keep joints full, about 10 mm for traditional bricks, and protect fresh work from frost and heavy rain. Thin-bed blocks need the manufacturer's thin-joint mortar instead.
Frequently asked questions
How much mortar per m² of brick wall?
About 45 kg of dry mortar for a half-brick wall and about 90 kg for a one-brick wall, with 1 cm joints.
Why does aerated concrete need so little?
Because the blocks are large and laid with 1–3 mm adhesive joints instead of 1 cm mortar joints.
What mortar mix for brickwork?
A common general-purpose mix is about 1:1:6 cement:lime:sand, or 1:5–6 cement:sand with a plasticiser; follow the masonry specification.
Can I lay bricks in cold weather?
Not when frost is expected within the setting time — frozen mortar loses strength. Protect fresh work with covers.