Bags of mortar for brick, block or repointing — with joint width as an input, because it changes the answer more than anything else.
Mortar Calculator
Inputs
3/8 in is standard for new work. Old buildings often have wider joints, and wide joints eat mortar fast.
On top of the trade figures, which already carry normal waste. Add more for cold weather or a long, broken-up job.
Results
Mortar needed
49 × 80 lb bags
bags = units ÷ (units per bag at joint width)
Calculated with BuildCalculators.com
Calculated with BuildCalculators.com · buildcalculators.com/mortar-calculator
Estimates are for planning only — confirm quantities with your supplier or contractor before ordering.
Mortar is the one masonry quantity where the geometry and the purchase order genuinely disagree, and the gap is big enough that quoting either number on its own misleads. The mortar sitting in the joints of a brick wall is about 0.008 cubic feet per brick. The figure every supplier and manufacturer quotes is 35 to 37 bricks per 80 lb bag — and a bag yields 0.7 cubic feet, so real consumption is 0.020 cubic feet a brick. Two and a half times the joint volume.
Neither number is wrong. The difference is waste, and mortar waste is enormous by the standards of any other material on a site: what drops off the trowel, what stiffens on the board, the bottom of the mixer, joints raked out and refilled. So this calculator buys against the empirical bag figures and shows you the joint volume separately, because knowing the gap exists is what stops you second-guessing the order.
The other thing it does that a fixed rule of thumb cannot: joint width. Going from a 3/8 inch joint to 5/8 takes brick from 37 a bag down to 27, and every published "bags per 1,000 brick" figure silently assumes 3/8.
144 ÷ ((unit length + joint) × (unit height + joint))37 − 38.4 × (joint − 0.375)13 − 16 × (joint − 0.375)units ÷ units per bag × (1 + allowance)ft² ÷ (37.5 − 60 × (joint − 0.5))A 3/8 inch joint is the standard for new work and the basis of every published figure. Widen it to 5/8 and two things happen at once: you need fewer bricks, because each one occupies more wall, and each brick eats far more mortar. The brick count falls about 12% while the mortar consumption rises around 35%. On repointing an old building the effect is larger still, because old joints are frequently 1/2 to 3/4 inch and the coverage per bag roughly halves across that range.
The model is anchored on published points rather than derived from geometry, precisely because geometry under-predicts by a factor of two and a half. Manufacturers and masonry suppliers agree on 35 to 37 modular bricks and 13 standard blocks per 80 lb bag at a 3/8 to 1/2 inch joint, dropping to about 25 bricks and 8 blocks at 5/8 to 3/4. The calculator interpolates between those points, so the answer stays anchored to what the trade actually observes at every joint width in between.
Pre-mixed mortar has the sand in the bag and is far easier for a small job. Masonry cement bought with sand separately is considerably cheaper by volume — roughly 7 bags of cement and a ton of sand per 1,000 brick, or 3 bags per 100 block. The crossover is around 300 units: below it the convenience wins, above it the price difference is real money and you are set up for a day of mixing regardless.
Type N is the general above-grade mortar and suits most residential work. Type S is stronger and belongs below grade or where the wall takes lateral load. Type M is stronger again and is for foundations and retaining walls. The instinct to reach for the strongest is exactly wrong: mortar should be weaker than the units it joins, so that when the wall moves — and it will — the crack runs through the joint, where it can be raked out and repointed, rather than through the brick, where it cannot be repaired at all.
Coverage for pointing assumes joints raked to about twice their width, so a 1/2 inch joint gets cut back 1 inch. Rake deeper and the figure falls quickly, because the void you are filling is much larger than the face suggests. More important than the quantity: on anything built before about 1930, match the old mortar rather than the colour. Hard Portland-based mortar in a soft old wall forces movement through the brick instead of the joint, and the faces spall off within a few winters. That usually means a lime mortar, and it is worth asking about before buying a single bag.
The published bag figures already carry ordinary waste — that is the whole reason they sit so far above the joint volume. The extra allowance on top is for the things they do not assume: cold weather, which shortens board life; a job broken across several days, where each session wastes a mixer bottom; and awkward work with many cuts and returns. On a straightforward warm-weather run, 10% is plenty.
Single wythe modular brick, no openings, pre-mixed mortar.
49 bags of 80 lb
The joints in that wall hold about 13 ft³ of mortar. You are buying 34 ft³. The difference is waste, and it is normal.
A wider joint — common on hand-made or reclaimed brick.
59 bags — ten more, on 188 fewer bricks
This is the whole argument for making joint width an input. A rule of thumb quoted per 1,000 brick would have got the brick count roughly right and the mortar badly wrong.
Old wall, joints averaging 5/8 in, raked to about 1¼ in deep.
9 bags of 80 lb
Far less than laying the same wall, because you are only filling the outer inch of each joint. Check what the existing mortar is before buying: a lime wall needs lime.
Units per square foot of wall, and units laid per 80 lb bag.
| Joint | Brick/ft² | Brick per bag | Block/ft² | Block per bag |
|---|---|---|---|---|
| 0.25 in | 7.31 | 41.8 | 1.152 | 15.0 |
| 0.375 in | 6.86 | 37.0 | 1.125 | 13.0 |
| 0.5 in | 6.44 | 32.2 | 1.099 | 11.0 |
| 0.625 in | 6.07 | 27.4 | 1.074 | 9.0 |
| 0.75 in | 5.73 | 22.6 | 1.050 | 7.0 |
Bags include a 10% allowance on top of the trade figures.
| Joint | Bricks | Bags | Blocks | Bags |
|---|---|---|---|---|
| 0.375 in | 1646 | 49 | 270 | 23 |
| 0.5 in | 1547 | 53 | 264 | 27 |
| 0.625 in | 1458 | 59 | 258 | 32 |
| Type | Strength | Where it belongs |
|---|---|---|
| N | 750 psi | General above-grade work — the default |
| S | 1,800 psi | Below grade, or walls taking lateral load |
| M | 2,500 psi | Foundations, retaining walls, paving |
| O | 350 psi | Interior and non-load-bearing repointing |
| Lime | Low, flexible | Historic masonry — soft brick and stone |
Pre-mixed mortar runs $7–$12 for an 80 lb bag in 2026, so a 30 by 8 ft brick wall is $340–$590 of mortar. Masonry cement is $12–$18 a bag and needs sand at $30–$60 a ton, which works out considerably cheaper on anything past a few hundred units — the crossover sits around 300 bricks or blocks.
On a brick wall the mortar is typically 5–10% of the material cost and a rounding error against the labour, which runs $10–$20 per square foot of wall laid. That is worth knowing before optimising the mortar order: the difference between pre-mixed and site-mixed on a small wall is perhaps $100, and running out mid-course costs more than that in lost time.
Not in the mortar, particularly — in the brick. A wall built at 5/8 inch joints uses about 12% fewer bricks than the same wall at 3/8, and brick is much dearer than mortar. Joint width is usually dictated by the unit and the look rather than the budget, but if you are working with reclaimed brick of variable size, the wider joint that makes the wall possible also makes it slightly cheaper.
Repointing runs $8–$20 per square foot of wall face done properly — raked out with a grinder or chisel, cleaned, and pointed in matching mortar. It looks expensive per square foot until you price rebuilding, which is several times that and loses the original brick. Where the mortar has failed but the units are sound, pointing is almost always the right answer.
Every published rule of thumb assumes 3/8 inch. At 5/8 the same wall needs about a fifth more mortar and a tenth fewer bricks. Measure an existing joint before ordering for repair work.
The joints hold roughly 40% of what you will actually use. Mortar waste is genuinely that high, and the trade bag figures already account for it — buying to the geometric volume leaves you badly short.
Mortar should be weaker than the units it joins. Type M in a soft brick wall moves the failure from the joint, which is repairable, into the brick face, which is not.
The single most common way to destroy a historic wall. Hard mortar traps moisture and forces movement through the masonry; the faces spall off within a few freeze cycles. Match the original, which usually means lime.
Mortar has a board life of about two hours in mild weather and much less in heat. Mixing a full batch for a slow day means throwing away the tail of it — and retempering stiffened mortar with more water weakens it permanently.
Masonry cement is cement only. It needs roughly a ton of sand per 1,000 brick, or a cubic yard per seven bags, and the sand has to be there before you start mixing.
About 27 bags of 80 lb pre-mixed at a 3/8 inch joint, since a bag lays roughly 37 modular bricks. Buying masonry cement and sand separately instead, the trade rule is about 7 bags of cement plus a ton of sand per 1,000 brick. Both figures assume a 3/8 inch joint — at 5/8 you need around a third more.
13 standard blocks per 80 lb bag of pre-mixed at a 3/8 to 1/2 inch joint, falling to about 8 at 5/8 to 3/4. On the masonry cement route it is roughly 3 bags of cement per 100 blocks, plus sand.
Because mortar waste is genuinely enormous. The joints in a brick wall hold about 0.008 cubic feet per brick; real consumption is around 0.020 — two and a half times as much. It goes on the ground off the trowel, stiffens on the board, sits in the bottom of the mixer, and gets raked out and refilled. Every published bag figure already assumes it.
Type N for general above-grade work, Type S below grade or where the wall takes lateral load, Type M for foundations and retaining walls. Do not default to the strongest: mortar should be weaker than the units it joins, so cracks run through the joint where they can be repointed rather than through the brick where they cannot.
About 37 square feet of wall face per 80 lb bag at a 1/2 inch joint, dropping to roughly 22 at 3/4 inch. That assumes joints raked to about twice their width; rake deeper and the coverage falls quickly.
On anything built before about 1930, usually not. Hard Portland-based mortar in a soft old wall forces movement through the brick instead of the joint, and the faces spall off within a few freeze cycles. Match the original, which normally means a lime mortar — ask before buying.
Roughly two hours in mild weather and considerably less in heat. Retempering stiffened mortar with more water weakens it permanently, so mix what you can lay rather than a full batch for a slow day.
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Installed cost by finish, material shown separately
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This calculator uses published constants from named industry sources, each asserted in an automated test that runs on every build. The formula is printed with the result above, and any correction we make is logged on the changelog.
It is a planning estimate. It does not replace an engineer, a site visit or a written quote — confirm quantities with your supplier before ordering.