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Mortar calculator: cement, sand and lime for bricks or blocks
Put in how many bricks or blocks you are laying and pick the mix. It works out the wet mortar (about 1kg a brick in a half-brick wall) and splits it into cement, lime or plasticiser, and building sand by the designation, so the joint ends up weaker than the brick, as it should.
What you need
Mortar
- Wet mortar (muck)
- 1100 kg1kg a brick, plus 10%Tarmac Blue Circle QA mortar yields
To order
- Cement (OPC), M4 at 1:6 with plasticiser
- 7 × 25kg bagsMarshalls BTB4; MPA Mortar Data Sheet 19
- Plasticiser (feb)
- 0.5 litres60 to 90ml per bag of cement
- Building sand (soft sand)
- 2 bulk bags (~800 kg)943kg. A bulk bag is about 800kg, not a tonneSelco; BMF bulk bag minimum 800kg
Round up to whole packs and bags. Figures include the wastage you chose and match TradeCalc in the app.
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In the app, TradeCalc hands these quantities straight to ProQuote with your regional material prices, and the customer gets a branded PDF. Free to download.
Or claim your free profile link nowHow the maths works
- Wet mortar is about 1kg a brick in a half-brick wall, and 1.3kg in a one-brick wall because of the collar joint between the skins (Tarmac Blue Circle QA mortar: 1,800 to 2,000 bricks per m³ half-brick). Blocks take 0.012m³ per m² of 100mm blockwork, 0.016m³ for 140mm and 0.024m³ for 215mm, at 10 blocks a square metre and 1,800kg a cubic metre.
- The mix is a designation. M4 (iii), 1:1:6 or 1:5 to 6 with plasticiser, is the general mix for facing brickwork and blockwork. M6 (ii) is for copings and cills, M12 (i) only for engineering bricks in retaining walls and manholes, and M2 (iv) internal only (Marshalls BTB4; MPA Mortar Data Sheet 19).
- Parts are by volume, split here by weight as a working figure: close enough to order by, the same way merchants quote it. Plasticiser replaces the lime at 60 to 90ml per bag of cement.
- The allowance covers what is left in the mixer, dropped on the scaffold and knocked off the joints. 10% is typical for a day on site.
- This is the same maths as the brick calculator, so the two always agree.
Worked example
1,000 bricks in a half-brick wall take about a tonne of wet mortar, 1,100kg with 10% extra. At M4 with plasticiser (1:6) that is 7 bags of cement, 0.5 litres of plasticiser and 2 bulk bags of building sand. At 1:1:6 with lime it is 6 bags of cement, 6 of lime and 2 bulk bags of sand.
Questions people ask
How much mortar do I need for 1,000 bricks?
About a tonne of wet mortar in a half-brick wall, 1.3 tonnes in a one-brick wall. At M4 with plasticiser that is roughly 6 to 7 bags of cement and just under a tonne of building sand, so one bulk bag and a few 25kg bags, or two bulk bags to be safe.
What is the right mortar mix ratio?
For ordinary facing bricks, M4: 1:1:6 cement:lime:sand, or 1:5 to 6 cement:sand with plasticiser. M6 (1:½:4½ or 1:3 to 4) for copings and cills. Only use 1:3 (M12) with engineering bricks in retaining walls or manholes. A mix stronger than the brick cracks the brick, not the joint.
Lime or plasticiser?
Both make the mortar workable. Lime gives a softer, more flexible joint that suits older and softer bricks; plasticiser is quicker and what most sites use. Never add washing-up liquid: it weakens the mortar.
How much mortar for blocks?
About 2.2kg a block for 100mm blocks, 2.9kg for 140mm and 4.3kg for 215mm, at 10 blocks a square metre. 100 blocks of 100mm take about 240kg with 10% extra.
Related calculators
How many bricks, blocks, bags of cement, lime and sand you need for a wall, with the right mortar designation, wastage, openings and packs.
Sand calculator: building sand and sharp sand in bulk bagsHow much building sand or sharp sand a job needs, in tonnes, bulk bags and 25kg bags: brickwork, blockwork, sand and cement render or a block paving laying course.
Block calculator: concrete blocks and mortar for a wallHow many concrete blocks a wall needs by block type and thickness, plus the cement, lime and sand for the mortar, wall ties and pallets.
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