How it works
The calculator first finds how many units you will lay, then divides by the number of units one bag lays, and rounds up.
Units (from area) = ⌈ Wall area × Units per area ⌉
Units per area (modular brick) = 6.75 per sq ft
Units per area (8 × 16 in block) = 1.125 per sq ft
Units per area (custom) = 1 ÷ ((Unit length + Joint) × (Unit height + Joint))
Bags = ⌈ Units × (1 + Extra ÷ 100) ÷ Units per bag ⌉
⌈ ⌉ means rounding up to the next whole number. For 100 sq ft of modular brick, that is 100 × 6.75 = 675 brick, and 675 ÷ 37 = 18.2, so 19 bags of 80 lb QUIKRETE Mortar Mix as a minimum.
Where the numbers come from
The units-per-area figures are the same ones used by the brick and concrete block calculators on this site. The Brick Industry Association’s Technical Note 10 lists 675 modular brick per 100 sq ft of single-wythe wall with ⅜ in joints. CMHA (formerly NCMA) TEK 4-2A gives 112.5 standard 8 × 16 in block per 100 sq ft of wall. A custom unit is counted from its actual face size plus one joint in each direction, so a UK brick of 215 × 65 mm with a 10 mm joint takes up 225 × 75 mm of wall, about 59.3 bricks per square meter.
The bag yield is the manufacturer’s own number. QUIKRETE’s data sheet for Mortar Mix (No. 1102) says that each 80 lb bag “will lay up to 37 standard bricks or 13 standard (8 in by 8 in by 16 in …) blocks”. CEMEX UK’s datasheet for Rugby General Purpose Mortar says that one 25 kg bag will produce enough mortar to lay about 25 standard house bricks. Other products differ, which is why the custom option asks for the yield instead of guessing it.
Why mortar estimates run short
Mortar is easy to underestimate. CMHA’s TEK 4-2A calls it, after grout, probably the most commonly misestimated masonry material, because site batching versus bagged mortar, unit tolerances, work stoppages and other variables can change the quantity a lot between similar jobs. The manufacturer yields are also stated as “up to” or “approximately”, which describes good conditions with full, even joints and little spilled mortar.
The BIA’s own mortar volumes in Technical Note 10 are theoretical and exclude waste. It recommends adjusting estimates for bond pattern, collar joints and other conditions. That is why this calculator lets you add an extra-mortar percentage. There is no single published figure that fits every job, so the default is 0 % and a note reminds you to choose your own allowance. Many people buy one or two bags more than the count and return unopened bags if the store allows it.
Brick versus block
A bag lays far fewer blocks than bricks because each block’s bed joint is much longer and its head joint much taller. QUIKRETE’s figures make the difference clear: 37 bricks or 13 blocks from the same 80 lb bag. CMHA notes that its block mortar rules of thumb assume face-shell bedding, where mortar goes only on the front and back shells of hollow units, not across the webs. Full bedding of hollow block uses more mortar than those figures.
Starting from a unit count
If you have already worked out how many bricks or blocks you need, switch to “Number of units” and enter that count. Use the count before the brick waste allowance if you can: broken bricks that never get laid don’t use mortar. If you only have the area, the calculator converts it with the same per-area rates as the brick and block calculators, so the two results agree.
What is not included
This tool does not estimate mortar for collar joints between wythes, grout for filled cores or bond beams, parging, stucco or the scratch and setting coats used for stone veneer. It also does not choose the mortar type or strength. Those come from the wall’s design, the product data sheet and local code. Treat the bag count as a shopping estimate, check the bag label for the yield of the exact product and size you are buying, and keep enough bags from the same batch on hand so the color of the joints stays consistent.
Worked example
Inputs
- Start from
- Wall area
- Wall area
- 100 sq ft
- Unit and bag
- Modular brick, 80 lb QUIKRETE bag (up to 37 brick)
- Extra mortar
- 0 %
Result
- Units per wall area
- 6.75 / sq ft
- Units laid
- 675
- Bags of mortar mix
- 19
Common mistakes
- Using a brick yield for block. A block bed is much longer and taller than a brick bed, so one bag lays far fewer blocks than bricks – QUIKRETE gives 37 bricks but only 13 blocks per 80 lb bag.
- Mixing up bag types. A bag of masonry cement is not a bag of premixed mortar. Masonry cement still needs sand, so its “bags per 1,000 brick” rules of thumb do not apply to a bag that already contains sand.
- Applying an 80 lb yield to a 60 lb or 25 kg bag. The yield scales with the bag; enter the figure printed for the size you are buying.
- Treating “up to” as an average. Joint thickness, full versus face-shell bedding, cores filled by accident and droppings all use more mortar than the best case.
- Forgetting extra for corners, collar joints and grouted cores. This tool counts mortar for laying units in a single wythe only.
Assumptions and limits
- Wall area is converted to units with BIA Technical Note 10’s 6.75 modular brick per square foot and CMHA TEK 4-2A’s 1.125 standard block per square foot; custom units use the actual size plus one joint each way.
- Units are rounded up to whole units before the bag count. Bags are rounded up to whole bags after the extra-mortar allowance.
- The bag yield is the manufacturer’s stated number of units per bag. Presets use the QUIKRETE Mortar Mix 80 lb figures; every other product needs its own figure.
- Single-wythe walls laid in running bond. Collar joints, grout fill, multi-wythe walls and decorative bonds are not included.
- This is a material quantity only. Mortar type, strength and wall design come from your plans, local code or a qualified professional.
Frequently asked questions
How many bricks does one bag of mortar lay?
It depends on the bag size, the mix and the brick. QUIKRETE’s data sheet says one 80 lb bag of its Mortar Mix lays up to 37 standard bricks or 13 standard 8 × 8 × 16 in blocks. CEMEX UK says one 25 kg bag of Rugby General Purpose Mortar lays about 25 standard house bricks. Always use the figure for your own product.
How many bags of mortar do I need for 1,000 bricks?
With QUIKRETE’s 80 lb Mortar Mix figure of up to 37 bricks per bag, 1,000 bricks need at least 1,000 ÷ 37 = 27.03, rounded up to 28 bags, before any extra for droppings. A smaller bag, a thicker joint or a less careful mason will push that up.
How many bags of mortar for 100 concrete blocks?
At QUIKRETE’s figure of up to 13 standard blocks per 80 lb bag, 100 blocks need 100 ÷ 13 = 7.7, rounded up to 8 bags as a minimum. Add an allowance for waste.
Is the BIA rule of eight bags per 1,000 bricks the same thing?
No. The Brick Industry Association mentions a masons’ rule of thumb that eight bags of masonry cement lay 1,000 modular brick, and calls it a very rough estimate that includes an unspecified amount of waste. Masonry cement is mixed with sand on site, so the rule does not apply to premixed mortar bags.
Can I use this for stone veneer?
Not really. Manufactured stone is set in a mortar bed on a scratch coat, and the mortar use depends on the stone profile and joint style. Use the coverage your stone or mortar manufacturer publishes, and see the stone veneer calculator for the stone itself.
Does the calculator choose the mortar type?
No. Type N, S or M mortar is chosen by the wall’s designer or local code for the application. This tool only counts bags for the yield you give it.
Sources
- QUIKRETE Mortar Mix (No. 1102) Product Data Sheet — The QUIKRETE Companies. "Each 80 lb (36.2 kg) bag of QUIKRETE Mortar Mix will lay up to 37 standard bricks or 13 standard (8 in by 8 in by 16 in [200 mm by 200 mm by 405 mm]) blocks."
- Technical Note 10 – Dimensioning and Estimating Brick Masonry — Brick Industry Association. Modular brick 3⅝ × 2¼ × 7⅝ in with ⅜ in joints, nominal 4 × 2⅔ × 8 in; 675 bricks per 100 sq ft (Table 4); waste "at least 5 percent".
- TEK 04-02A – Cost Estimating Guide for Concrete Masonry — Concrete Masonry & Hardscapes Association (formerly NCMA). Nominal 8 × 16 in face = 8/9 sq ft per unit; 112.5 units per 100 sq ft before waste, 119 with a 5 % allowance.
- Rugby General Purpose Mortar – Datasheet — CEMEX UK. Coverage guide: "Approximately 1 x 25kg bags will produce enough mortar to lay 25 standard house bricks."
- Brindle 65mm – Data Sheet — Forterra (London Brick). UK brick "Standard work size 215 x 102.5 x 65mm", manufactured to BS EN 771-1.
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 3, 2026