Mortar is installed as a volume but a preblended product is bought by the bag, so a reliable order needs the finished yield printed by that product's manufacturer. The tool above turns masonry face area, wall thickness, a dimensionless mortar share and finished mortar yield per premix bag into a whole bag count. It does not treat binder-only masonry cement as premix. This page traces each input and the arithmetic so a surprising result can be checked before ordering.
What the three volume inputs multiply together
The tool multiplies masonry face area by wall thickness and a dimensionless mortar share. Read that product in two steps. Face area times wall thickness is the volume of the wall itself, so a 20 square meter panel across a 102 millimeter wythe is 2.04 cubic meters of wall. The mortar share states what fraction of that wall volume is mortar rather than brick. The shipped default of 0.164 means 16.4 percent; it is not a joint measurement in meters or inches and it stays 0.164 in either unit system. Brick Industry Association Technical Note 10 lists 5.5 cubic feet of mortar per 100 square feet for modular brick at a 9.5 millimeter joint, which works out to 0.0168 cubic meters per square meter, or 16.8 liters per square meter. Across a 102 millimeter wythe that is a share near 0.164. Enter the share, then check the answer against the cubic feet column before ordering.
Measuring the wall before you touch the bag count
- Net masonry face area. Run the tape along the finished brick face, not along the room behind it, and multiply length by height for each panel. Subtract every door, window and vent opening, because the wall area method starts from gross area less openings. Record the total in square meters. Tool: Tape measure.
- Bedded wythe thickness. Measure across the bed of a single course at an opening jamb or a wall end, where the full bedded width is visible. A nominal 4 inch modular wythe measures 102 millimeters. Keep any second wythe and its collar joint as separate figures rather than adding them here. Tool: Folding rule.
- Average joint thickness on the coursing. Mark ten courses on the face, measure the total height, subtract ten brick heights and divide the remainder by ten. One joint read alone carries the trowel variation of that single course. Compare the answer with the 9.5 and 12.7 millimeter columns of the quantity table. Tool: Joint gauge.
- Mortar share for the entry field. Take the cubic feet per 100 square feet figure that matches your brick and joint, convert it to cubic meters per square meter, then divide by the wythe thickness in meters. That dimensionless quotient, near 0.164 for modular brickwork, is what belongs in the mortar share field in both unit systems. Tool: Notepad.
- Finished yield per premix bag. Photograph the bag label or product data sheet rather than trusting a remembered figure. Enter its finished yield in liters per premix bag for Metric or cubic feet per premix bag for Imperial. If the manufacturer publishes only brick coverage or the product is binder-only masonry cement, do not invent a volume yield. Tool: Phone camera.
| Brick and nominal size (inches) | Joint thickness | Brick per 100 sq ft | Mortar per 100 sq ft (cu ft) | Mortar per 1000 brick (cu ft) |
|---|---|---|---|---|
| Modular, 4 by 2 2/3 by 8 | 9.5 mm (3/8 inch) | 675 | 5.5 | 8.1 |
| Modular, 4 by 2 2/3 by 8 | 12.7 mm (1/2 inch) | 675 | 6.9 | 10.3 |
| Engineer Modular, 4 by 3 1/5 by 8 | 9.5 mm (3/8 inch) | 563 | 4.8 | 8.5 |
| Engineer Modular, 4 by 3 1/5 by 8 | 12.7 mm (1/2 inch) | 563 | 6.1 | 10.8 |
| Closure Modular, 4 by 4 by 8 | 9.5 mm (3/8 inch) | 450 | 4.1 | 9.1 |
| Roman, 4 by 2 by 12 | 9.5 mm (3/8 inch) | 600 | 6.4 | 10.7 |
| Norman, 4 by 2 2/3 by 12 | 9.5 mm (3/8 inch) | 450 | 5.1 | 11.2 |
| Utility, 4 by 4 by 12 | 9.5 mm (3/8 inch) | 300 | 3.7 | 12.3 |
Source: Brick Industry Association, Technical Note 10: Dimensioning and Estimating Brick Masonry.
Figures exclude waste, collar joints and bond pattern corrections. The same document advises adding 15 to 25 percent to the net mortar quantity and at least 5 percent to the net brick quantity.
Running the shipped defaults end to end
| Field | Value |
|---|---|
| wallArea | 20 |
| mortarShare | 0.164 |
| wallThickness | 0.102 |
| bagYield | 20.38812954624 |
| waste | 15 |
Start with the defaults. Twenty square meters of face area times the 0.102 meter wythe gives 2.04 cubic meters of masonry. Multiplying by the dimensionless 0.164 mortar share gives 0.33456 cubic meter of mortar. The 15 percent allowance at the bottom of BIA's published band raises that to 0.384744 cubic meter. The Ash Grove Type S example yield is 0.72 cubic foot, exactly 20.38812954624 liters or 0.02038812954624 cubic meter, per 80 pound bag. The raw requirement is 18.87098 and the order rounds up to 19 bags. Imperial mode shows the source value of 0.72 cubic foot per bag and produces the same result. At 20 percent waste the raw requirement is 19.69146 and still rounds to 20 bags. The share remains 0.164 in both systems; replace the yield with the exact product data before buying.
Result: 19 bags.
Common mistakes
- Typing 0.01 into the mortar share field as though it were a 10 millimeter bed depth.
- The field is multiplied by the wall volume, so 0.01 states that one percent of the wall is mortar, about one liter per square meter, while Technical Note 10 gives 16.8 liters per square meter for modular brickwork at a 9.5 millimeter joint. Enter the mortar share instead, near 0.164 for a 102 millimeter wythe, and confirm the bag count against the cubic feet per 100 square feet column of the same table.
- Reducing the default waste allowance below the published mortar band without a job-specific takeoff.
- BIA publishes 15 to 25 percent added after the correction factors, so an unexplained 10 percent entry sits below the bottom of that band before a single joint is raked or a board scraped. Keep the 15 percent default at the bottom of the cited band unless the mason documents another figure; use the higher part of the band when site conditions justify it, and keep brick breakage separate.
- Ordering preblended mortar mix against a masonry cement bag count.
- The eight bags per 1000 modular brick rule describes binder-only masonry cement that is proportioned with separate sand, while this calculator divides finished mortar volume by a preblended product's published finished yield. One product cannot be substituted for the other by changing a weight. Use this bag count only for a premix whose manufacturer states finished volume per bag. For masonry cement, follow the specified cement-sand mix schedule and obtain the separate material take-off from the manufacturer or mason.
- Mixing every bag at once so the mortar board never runs dry.
- ASTM C270 requires all mortar to be used within 2.5 hours of mixing, and within 2 hours in hot weather, so a large early batch is discarded and reappears later as an unplanned second delivery. Split the bag count into batches sized for about two hours of laying, and store the remaining bags dry and off the ground until the mixer is ready for them.
- Applying single wythe figures to a wall with a mortared collar joint.
- A 9.5 millimeter collar joint adds 3.13 cubic feet per 100 square feet, which is 0.0095 cubic meters per square meter, and that sits entirely outside the single wythe quantity table. Add the collar volume as its own figure, about 0.19 cubic meters across a 20 square meter wall, or raise the share so the total matches both wythes plus the joint between them.
Reading finished yield from the exact premix bag
The yield field is a finished mortar volume per preblended bag, not the bag's weight. Ash Grove Packaging's own quantity chart lists its Type S Mortar Mix under ASTM C270 and publishes 0.72 cubic foot of mortar for one 80 pound bag in modular brickwork, with about 35 to 40 modular units per bag. The calculator keeps 0.72 cubic foot as the source value and uses its exact physical equivalent, 20.38812954624 liters, in Metric mode. That yield belongs only to the named product and application; another premix needs its own current manufacturer yield. General Mortar Mix No. 1102 publishes brick and block coverage rather than a finished volume, so no liter-per-bag value should be invented for it.
Waste, bond pattern and collar joint corrections
The order of operations matters. Technical Note 10 asks for net quantities first, then correction factors, then waste. Bond pattern comes first: common bond with full headers every fifth course adds one fifth to the brick count and one fifteenth to the mortar, every sixth course adds one eighteenth of mortar, English bond adds one sixth, and Flemish bond adds one ninth. A mortared collar joint between wythes is separate again, and Technical Note 10 gives 3.13 cubic feet per 100 square feet for a 9.5 millimeter collar joint, which is 0.0095 cubic meters per square meter, or about 0.19 cubic meters across a 20 square meter wall. Hollow units laid with face shell bedding cut the figure instead, by a percentage equal to the void percentage, typically 25 to 35 percent, while coring up to 25 percent of the bedded area still counts as solid. Only then comes waste, and the published band is 15 to 25 percent for mortar and at least 5 percent for brick.
Choosing a mortar type before trusting a product yield
ASTM C270 sorts masonry mortar into Types M, S, N and O. Under the property specification the 28 day minimum compressive strengths are 2500 pounds per square inch for Type M, 1800 for Type S, 750 for Type N and 350 for Type O, which is 17.2, 12.4, 5.2 and 2.4 megapascals. Minimum water retention is 75 percent for all four. Maximum air content is 12 percent for cement lime Types M and S, 14 percent for Types N and O, and 18 or 20 percent once mortar cement or masonry cement is used. Stronger is not automatically better, and the Brick Industry Association recommends Type N for normal use including most veneer, with Type M kept for exterior paving and Type S accepted as an alternative for interior paving. Brick suction changes the choice as well: units with an initial rate of absorption above 30 grams per minute per 194 square centimeters should be wetted 3 to 24 hours ahead and laid surface dry, and those recommendations are written for laying temperatures of 4 to 37.8 degrees Celsius.
Frequently asked questions
How many bags does 20 square meters of brickwork really need?
Using the published figure of about 5.5 cubic feet per 100 square feet for modular brick at a 9.5 millimeter joint, this 20 square meter example uses 0.33456 cubic meter before waste. The 15 percent default raises that to 0.384744 cubic meter. Dividing by Ash Grove's product-specific 0.72 cubic foot yield, exactly 0.02038812954624 cubic meter, gives 18.87098, so the tool orders 19 whole bags. Replace that yield with the current value for the exact premix and application.
Is masonry cement the same as a bag of mortar mix?
No. Masonry cement is binder only and is proportioned on site with separate sand, so it has no interchangeable finished-volume value for this premix calculation. Technical Note 10's eight bags per 1000 modular brick is a rough field rule for that different purchasing method. Use this calculator only when a preblended product publishes finished yield per bag. Otherwise follow the specified cement-sand mix schedule and ask the manufacturer or mason for the separate take-off.
Which mortar type suits ordinary brick veneer?
The Brick Industry Association recommends Type N for normal use, including most veneer work, and Type S is treated as an acceptable alternative where the compressive strength requirement is met. Type M is kept for most exterior paving. Under the property specification Type N reaches a minimum of 750 pounds per square inch, or 5.2 megapascals, at 28 days, while Type M reaches 2500 pounds per square inch. Higher strength does not improve bond, which is the property that governs veneer performance.
Should the brick be wetted before laying?
It depends on suction. Mortar bonds best to brick with an initial rate of absorption of 30 grams per minute per 194 square centimeters or less at the moment of laying. Above that value the brick should be wetted 3 to 24 hours before laying and then laid surface dry, so that standing water on the face does not float the unit. Those recommendations are written for laying temperatures between 4 and 37.8 degrees Celsius, and colder or hotter work needs different handling.
When should a mason or engineer take the numbers over?
Treat the bag count as a purchasing figure only. Reinforced or loadbearing masonry, foundation and retaining walls, chimneys, parapets, and any work in seismic or high wind regions are designed under building code rules that set the mortar type, the bedding and the reinforcement, and none of that is decided by a quantity estimate. Bring in a mason for the mix schedule and a design professional wherever the wall carries load or retains soil.
Related calculators
Sources
- Technical Note 10: Dimensioning and Estimating Brick Masonry Brick Industry Association. Table 4 supplies the brick counts and the 5.5, 6.9, 4.8, 4.1, 6.4, 5.1 and 3.7 cubic feet per 100 square feet figures used in the data table, Table 5 the 3.13 cubic feet collar joint figure, Table 6 the bond pattern factors, and the text the 15 to 25 percent mortar waste band and the eight bags per 1000 brick rule. Accessed 2026-09-06.
- Technical Note 8: Mortars for Brickwork Brick Industry Association. Supplies the ASTM C270 property requirements quoted on this page, including the 2500, 1800, 750 and 350 pounds per square inch minimums, the 75 percent water retention minimum, the 12, 14, 18 and 20 percent air content limits, the 2.5 hour working time, and the brick suction threshold with wetting 3 to 24 hours before laying. Accessed 2026-09-06.
- Technical Note 8B: Mortars for Brickwork, Selection and Quality Assurance Brick Industry Association. Supports the mortar type guidance on this page, meaning Type N recommended for normal use including most veneer, Type S accepted as an interchangeable alternative, Type M kept for most exterior paving, the mortar type table indexed on brick suction, and the 4 to 37.8 degree Celsius laying range those recommendations assume. Accessed 2026-09-06.
- Product Quantity Calculator and Masonry Quantity Charts Ash Grove Packaging. Manufacturer quantity chart supplying the product-specific default: Type S Mortar Mix under ASTM C270, 80 pound bag, 0.72 cubic foot of mortar and about 35 to 40 modular brick units per bag. Accessed 2026-09-07.
- Mortar Mix No. 1102 Data Sheet QUIKRETE. Demonstrates why yield cannot be assumed across products: this general brick and block mortar sheet publishes coverage per bag rather than a finished volume, so the calculator requires a different product's explicit volumetric yield. Accessed 2026-09-07.
This is a planning result, not a supplier quote; sellers use different pack, bag, board, roll, and bundle conventions, so confirm the exact product label and selling unit before you order.