Mix right.
Bags of mortar mix for brick, block, and stone walls. Accounts for joint width, brick size, and mortar type so you order the right amount.
How we calculated this
Mortar volume per unit is calibrated to manufacturer published coverage rather than to nominal joint geometry alone. Geometry alone suggests about 13 cubic inches per modular brick, but real masonry consumes closer to 30 once furrowed bed joints, generously buttered head joints, and board loss are counted, which is why Quikrete publishes 37 bricks per 80 lb bag and Sakrete about 40.
An 80 lb bag of premixed mortar yields about 0.6 cubic feet, or 1,037 cubic inches, which lays roughly 35 standard bricks or 13 concrete blocks at 3/8 inch joints. These are manufacturer published coverage rates and already account for the extra mortar real masonry consumes over nominal joint geometry.
A 5 percent margin is added on top. It is deliberately modest because the per-unit volumes already carry the waste built into manufacturer coverage figures; adding a further 10 to 15 percent would double count it.
Mortar type (S, N, M) does not change the volume calculation. All three types yield the same volume per bag. The type affects bond strength, compressive strength, and weather resistance. Type S is the default for exterior residential masonry.
Concrete block uses far more mortar per unit than brick because each unit has much longer joint lines. A standard 8x8x16 block takes roughly 80 cubic inches at a 3/8 inch joint, so one 80 lb bag lays about 13 blocks against 35 bricks.
Mortar is not grout, and the difference matters
People search for "mortar calculator" and land on grout calculators. The two products are not interchangeable. Mortar bonds bricks, blocks, or stones together. It contains Portland cement, lime, and sand in a ratio that gives it body and adhesion. Grout fills the narrow joints between tiles. It contains cement and fine aggregate with no lime, formulated to flow into thin gaps. Using grout between bricks creates a weak bond that crumbles within a year. Using mortar between tiles leaves a rough, oversized joint that looks terrible and traps dirt. The calculator above is specifically for mortar: bed joints and head joints in masonry walls.
If your project involves tile, use the grout calculator instead. If it involves bricks, blocks, or stone, you are in the right place.
How we calculated these numbers▾
Coverage is calibrated to manufacturer published rates rather than to nominal joint geometry alone. Joint geometry suggests roughly 13 cubic inches of mortar per modular brick, but real masonry consumes closer to 30 once furrowed bed joints, generously buttered head joints, and board loss are included, which is why Quikrete publishes 37 bricks per 80 lb bag and Sakrete about 40. This calculator uses 35 bricks or 13 concrete blocks per 80 lb bag at a 3/8 inch joint, with a 5 percent margin on top. Mortar type proportions follow ASTM C270.
Choosing the right mortar type
The type designation is not a quality grade. Type M is not "better" than Type S. Each is formulated for a specific application. Type S has the best balance of bond strength and flexibility, making it the default for exterior walls, chimneys, and any structural masonry above grade. Type N has lower compressive strength but higher workability, which makes it easier to tool and better for interior accent walls and veneer where structural load is not a concern. Type M has the highest compressive strength (2,500 psi) but the lowest bond strength, which makes it the wrong choice for walls exposed to wind load but the right choice for retaining walls and foundations where compressive force dominates.
Type O, repointing, and the mnemonic worth knowing
There is a fourth type most tables leave out. Type O is a low strength mortar at roughly 350 psi, soft enough to be sacrificial, and it exists for one job: repointing old masonry. Historic brick is softer than modern brick, and filling its joints with a hard modern mortar transfers stress into the units themselves, which then spall and crack. The mortar is supposed to be the weakest part of the wall so that it fails first and can be replaced. Repointing a nineteenth century wall with Type S is a common and expensive mistake.
The order is easy to remember once you see it. Write out MASON WORK and take every other letter: M, S, N, O, K. That is the sequence from strongest to weakest, and Type K, softer still at around 75 psi, is reserved for genuine historic restoration under a conservator's direction.
Strength | Proportions | Where it belongs | |
|---|---|---|---|
| Type M | 2,500 psi | 1 : 0.25 : 3.5 | Below grade, foundations, retaining walls |
| Type S | 1,800 psi | 1 : 0.5 : 4.5 | Exterior at or near grade, chimneys, patios |
| Type N | 750 psi | 1 : 1 : 6 | General above-grade exterior and interior |
| Type O | 350 psi | 1 : 2 : 9 | Repointing older masonry, interior non-load-bearing |
ASTM C270 mortar types by strength and job. Proportions are cement to lime to sand by volume, which is what a site mix follows when premixed bags are not used.
Thinset is tile mortar, not masonry mortar
Searches for thinset mortar and thinset tile mortar land on mortar pages constantly, and the two products are not interchangeable. Masonry mortar bonds brick and block into a wall and is specified to ASTM C270. Thinset is a cement, sand, and polymer adhesive that bonds tile to a substrate, specified to ANSI A118.1 for unmodified and A118.4 for modified. It is applied in a thin notched layer rather than a bed joint, and it will not build a wall.
Coverage is also calculated differently. Masonry mortar is estimated per brick or block; thinset is estimated per square foot by trowel notch size. A 50 pound bag covers roughly 90 square feet at a 1/4 by 1/4 inch notch, about 45 at 1/2 by 1/2, and closer to 30 with large format tile where back-buttering is required. If you are setting tile, the tile calculator and the grout calculator are the right tools; this page is for the mortar that holds masonry units together.
How many bags for your wall
Bricks | 80 lb bags | |
|---|---|---|
| Small garden wall, 50 ft² | 350 | 11 |
| Fence-height wall, 100 ft² | 700 | 21 |
| Garage wall, 200 ft² | 1,400 | 42 |
| House wall, 400 ft² | 2,800 | 84 |
Bags for common wall sizes in modular brick at 3/8 inch joints, including a 5 percent margin. Concrete block walls of the same area take roughly three times as many.
Composite illustration based on typical project dimensions, regional contractor pricing, and 2026 material costs. Not a specific real project.
Mixing mortar correctly
The consistency you want is often described as "peanut butter": thick enough to hold its shape on the trowel when you flip it upside down, but wet enough to spread easily into a bed joint. Too dry and the mortar will not bond to the brick surface. Too wet and it squeezes out of the joint and runs down the wall face, staining the brick. Start with about 5 quarts of water per 80-lb bag and adjust by small amounts. The correct consistency depends on temperature and humidity. Hot dry days require slightly more water. Cold damp days require less.
Pre-mixed bags | Site-mixed | |
|---|---|---|
| Cost per bag equiv. | $7 to 10 | $4 to 6 |
| Consistency | Reliable batch to batch | Varies with proportioning |
| Best for | Under 500 bricks, DIY | Large jobs, experienced masons |
| Mixing | Add water only | Proportion cement + lime + sand |
| Shelf life | 12 months sealed | Cement: 3 months, sand: indefinite |
For residential projects, pre-mixed bags are the standard. The cost premium over site-mixed is small and the consistency is guaranteed.
How mortar quantity connects to brick quantity
The brick calculator estimates brick count and includes a mortar line item. This mortar calculator gives you a more detailed breakdown with mortar type selection and mixing guidance. For projects that need both tools, start with the brick calculator for the brick count, then use this calculator to verify the mortar quantity with your specific joint width and mortar type.
For the concrete footings under a brick wall, the concrete calculator handles footing volume. For reinforcement in the footing or within a block wall (rebar in filled cores), the rebar calculator estimates bar count and total length.
Frequently asked
How many bags of mortar do I need per 1,000 bricks?
About 30 bags of 80 lb mortar per 1,000 standard bricks at 3/8 inch joints, since one bag lays roughly 35 bricks. Half inch joints raise it to about 40 bags. Concrete block uses far more: roughly 77 bags per 1,000 units, because the joints are much longer.
What is the difference between Type S, Type N, and Type M mortar?
Type S is the default for exterior walls and structural applications: it has the best bond strength and weather resistance. Type N is for interior and above-grade non-structural work. Type M has the highest compressive strength and is used below grade (retaining walls, foundations).
Can I use mortar instead of grout?
No. Mortar bonds bricks or blocks together and has sand for body. Grout fills joints between tiles and is much thinner. They are different products with different formulations. Use the grout calculator for tile projects.
How long does a bag of mortar last once opened?
Unopened bags last about 12 months in dry storage and opened bags one to two months. ASTM C270 sets a 2.5 hour board life for mixed mortar. Retempering with a small amount of water to replace evaporation is acceptable within that window; adding water to mortar that has begun to stiffen from hydration is not, and permanently weakens the bond.
Sources
- ASTM C270: Mortar for Unit Masonry - The specification defining Types M, S, N, O, and K and their proportions
- BIA Technical Note 8: Mortars for Brickwork - Mortar selection by exposure and the case against overly strong mortar
- Portland Cement Association: Masonry Mortar - Mixing practice, retempering limits, and cement to lime ratios
- NPS Preservation Brief 2: Repointing Mortar Joints - Why historic masonry requires soft mortar and how to match an existing mix
- Quikrete and Sakrete: Mortar Mix Coverage Data - Published bag coverage of 37 to 40 bricks or about 13 blocks per 80 lb bag, which this calculator is calibrated to
- ANSI A118.4: Modified Dry-Set Cement Mortar - The separate standard governing thinset, which is tile adhesive rather than masonry mortar
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