How Much Mortar Do I Need?
Mortar is sized off the unit count and the joint. Here are the rules of thumb for brick and block, how many bags of mortar mix to buy, the sand and cement if you mix your own, and which mortar type (N, S, M or O) to use.
By the Calculate My Reno Team / Published
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Mortar is sized off the unit count and the joint, not the wall area directly: more units, thicker joints or deeper beds all mean more mortar. You can buy it two ways - ready-mixed by the bag, or site-mixed from cement and sand - and the figures below cover both.
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The brick calculator and concrete block calculator both estimate the mortar volume from your unit size and joint, then give the bags of mortar mix and the sand volume alongside the unit count. This guide is the rules of thumb behind those numbers.
The rules of thumb
brick: ~0.3 m³ mortar per 1,000 bricks
block: ~4 cu ft (face-shell) to ~8.5 cu ft (solid bedding) per 100 block
bags: premixed mortar mix ~0.5 cu ft each (~12 block or ~45 brick per 80 lb bag)
masonry cement (you add sand): ~3 bags / 100 block, ~7 bags / 1,000 brick
sand (if mixing): ≈ the mortar volume cement: at 1 : 3-4 with the sand
Mortar fills the joint fraction of the wall through the bed of the unit. Brick joints are thin so the mortar per brick is small; block beds are deep so each block uses far more, even though a wall has far fewer blocks. Frogged (indented) or cored units and fuller joints push the figure up, which is why the calculator adds your waste allowance.
Mortar by job size
Approximate bags of masonry cement (you add sand), brick and block, before waste:
| Job | Units | Masonry cement bags |
|---|---|---|
| Small garden wall | 500 bricks | ~4 |
| Single-skin house wall | 2,000 bricks | ~14 |
| Block garage | 200 block | ~6 |
| Block foundation | 400 block | ~12 |
These are masonry cement bags (mix with sand). Premixed mortar-mix bags are smaller (~0.5 cu ft / 20 kg each), so a job needs roughly 2–3× as many — the count the calculators give.
Which mortar type to use
| Type | Strength | Use it for |
|---|---|---|
| N | ~750 psi | General above-grade brick and block - the default |
| S | ~1,800 psi | Below-grade, foundations, retaining and exterior at-grade |
| M | ~2,500 psi | Heavy load, below-grade, stone and driveways |
| O | ~350 psi | Interior, non-load-bearing, repointing soft old brick |
When in doubt above ground, Type N; below ground or for a retaining wall, Type S. Matching an old soft brick wall for repointing usually means a softer Type O or a lime mortar, not a hard modern mix.
Mixing your own: sand and cement
The handy rule is that the volume of damp sand you need is about the volume of finished mortar - the cement paste fills the voids between the sand grains, so it does not add much bulk. Mix roughly 1 part cement to 3 to 4 parts sand by volume (a plasticiser or lime improves workability). So take the mortar volume from the calculator, buy that much sand, and add cement at your ratio.
Worked example
A wall of 1,500 modular bricks, 10 mm joints:
- Mortar: 1,500 ÷ 1,000 × 0.3 m³ = 0.45 m³ (about 16 cu ft).
- Bags of mortar mix at ~0.5 cu ft each: 16 ÷ 0.5 = about 32 bags, plus a little for waste.
- Site-mixing instead: about 0.45 m³ of sand plus cement at 1:4.
Round mortar up - it is cheap next to running short mid-course. For the unit counts that drive this, see how many bricks do I need and how many concrete blocks do I need; for how mortar differs from concrete, mortar vs concrete.
Frequently asked questions
How much mortar do I need per 1000 bricks?
Roughly 0.3 cubic metres of mortar per 1,000 standard bricks laid with a 10 mm joint. That is about 21 bags of premixed mortar mix (a bag lays roughly 45 brick), or about 7 bags of masonry cement plus around 0.3 m³ of sand if you mix your own. Frogged or cored bricks and fuller joints use more, so treat it as a starting point and round up.
How many bags of mortar do I need per 100 block?
About 4 cubic feet of mortar per 100 standard 8 × 8 × 16 in blocks with face-shell bedding (the figure the calculators use) - roughly 8 bags of premixed 80 lb mortar mix, since a bag lays about a dozen blocks, or about 3 bags of masonry cement plus sand if you site-mix. Full (solid) bedding uses up to twice as much, about 8.5 cubic feet per 100. The calculator estimates the volume from your block size, joint and bag size and gives the bag count.
What is the difference between type N, S and M mortar?
They differ in strength and where they are used. Type N (about 750 psi) is the general-purpose mix for most above-grade brick and block. Type S (about 1,800 psi) is stronger, for below-grade, foundations and retaining walls. Type M (about 2,500 psi) is the strongest, for heavy loads and below-grade masonry. Type O is a soft, low-strength mortar for interior and repointing of old soft brick.
How much sand and cement do I need for mortar?
A common brick mortar is about 1 part cement to 3 or 4 parts sand by volume. The volume of damp sand you need is roughly the volume of finished mortar, because the cement paste fills the gaps between the sand grains - so size the sand off the mortar volume, then add cement at the chosen ratio. The calculator gives the mortar volume and the sand; add masonry or Portland cement to suit your ratio.