Brick Mortar Calculator How Many Bags
Underestimating mortar turns a Saturday morning project into a Tuesday afternoon. The math is small but it adds up fast: every 100 modular bricks needs roughly 5 to 7 cubic feet of wet mortar, the type of mortar changes that number, and the bag yield is not the same for an 80 lb sack as it is for a 60 lb sack. This guide gives you the per-1000-brick baseline, the bag-yield table for the three most common mortar types, and a worked example so you can order exactly what the wall will drink and not pay to haul leftovers.
How much mortar a brick wall actually uses
Mortar is the glue between bricks, and the wall wants surprisingly little of it. A standard modular brick laid in a running bond leaves only about a 3/8-inch mortar joint on the bed and the head. Multiply that by the number of bricks and you get a small volume — the rest of the wall is brick, not mud. A good rule of thumb is 5 to 7 cubic feet of wet mortar per 1,000 modular bricks, depending on joint profile, waste, and brick core holes that swallow extra mud.
Bag counts by mortar type
Mortar is graded by ASTM C270 into Types N, S, and M based on compressive strength and use case. Type N is the everyday exterior-above-grade workhorse; Type S is stronger and used at foundation walls and below-grade; Type M is the strongest, used for heavy retaining walls and paving. Yields per bag are close because the cementitious content is similar — the bag count by type is roughly the same; what differs is the wall location.
| Mortar type | Typical use | 80 lb bag yield (cu ft) | 80 lb bags per 1,000 bricks | 60 lb bags per 1,000 bricks |
|---|---|---|---|---|
| Type N | Exterior above-grade, general brickwork | 0.75 - 0.80 | 7 - 9 | 10 - 12 |
| Type S | Below-grade, foundation walls, wind-prone areas | 0.70 - 0.80 | 7 - 9 | 10 - 13 |
| Type M | Retaining walls, heavy loads, paving | 0.65 - 0.75 | 8 - 11 | 11 - 14 |
Add 10% waste for typical conditions; 15% if the bricks are irregular, the joints are heavy, or you are laying in cold weather and re-mixing often.
The brick-mortar formula
The 0.006 cu ft per brick factor is calibrated to a standard 3/8-inch bed joint and a 3/8-inch head joint. Larger joints push the volume higher; tighter joints save a small amount. Block walls use far less mortar per unit (because the cores are larger than brick voids), so for a concrete block project use the block calculator instead.
Worked example: a 10x10 garden brick wall
Picture a single-wythe garden wall, 10 feet long and 6 feet tall, laid with standard modular bricks (about 7.5 bricks per square foot of wall face). That is roughly:
Round up; you would order 4 to 5 bags of 80 lb Type N for this small wall. If you were laying the same wall in Type S for a stronger bond, the bag count is the same within one bag.
Bagged mortar vs. sand-and-cement on-site mix
| Option | Pros | Cons | Best for |
|---|---|---|---|
| Pre-mixed 80 lb bag (Type N/S/M) | Consistent ratio, no sand sourcing, fast setup | Most expensive per cubic foot, bag waste | Small walls, repairs, DIYers |
| Bulk sand + Type N masonry cement (on site) | Lowest cost per cu ft, fresher mix | Requires mixing tub or mortar mixer, ratio errors | Masonry contractors, larger walls |
| Pre-blended mortar mix + sand additive | Middle-cost, no masonry cement to source | Ratio still matters; read the bag carefully | Most DIY walls under 1,000 bricks |
Pre-mixed bags win on convenience for walls under about 1,500 bricks. Beyond that, the per-bag savings from a bulk mix more than cover the cost of a small electric mortar mixer.
Common mistakes
- Forgetting waste: droppings and re-tempering push real-world use 10-15% above the theoretical figure.
- Wrong mortar type: Type O is too soft for exterior walls; Type M is too stiff for brick and can crack.
- Cold weather shortcuts: below 40°F, mortar needs warm water and longer cure; never lay on frozen brick.
Get the exact count
Plug your wall dimensions and brick size into the Mortar Calculator for the precise bag count with waste built in. If your wall ties into a concrete footing or uses block instead of brick, those calculators handle the math separately so the whole assembly comes out right.