How to Calculate Brick and Mortar Quantity

Bricks per square foot

The Brick Industry Association (BIA) calls the wall-area method the most widely used way to estimate brick: multiply the net wall area (the gross area less openings) by the quantity of brick and mortar needed per square foot. For standard modular brick with ⅜ in joints, BIA Technical Note 10 gives 675 bricks per 100 ft², or 6.75 bricks per ft².

Many online calculators say about 7 instead. They add a ⅜ in joint to the brick's 2¼ in height and 7⅝ in length, giving 144 ÷ (8 × 2⅝) ≈ 6.86, and round up. Modular brick is laid so that three courses measure 8 in, so each brick and its joint occupy 8 × 2⅔ in of wall: 144 ÷ (8 × 2⅔) = 6.75. On a 200 ft² wall, 7 per square foot overestimates by 50 bricks before waste.

Brick and mortar by brick size

Net quantities from BIA Technical Note 10, Table 4, for ⅜ in joints in running or stack bond. They don't include waste.

Waste: bricks and mortar are different

BIA's procedure is to work out net quantities first and then add waste. For brick, its general rule is to add at least 5% to the net quantity delivered to the jobsite, and more where job conditions or experience warrant. For mortar, it suggests adding 15 to 25% to the net quantity.

The Brick Calculator starts at 5% and applies that one allowance to both its brick and its mortar output. For the mortar order, use the Mortar Calculator and set its allowance between 15% and 25%.

Bond pattern and wall thickness

BIA's Table 4 assumes running or stack bond. Patterns with header courses use more brick and mortar: BIA's correction factors add ⅙ to the brick count and 1/18 to the mortar for common bond with full headers every sixth course, and ½ and ⅙ for English bond. If the collar joint between two wythes is filled solid, BIA's Table 5 adds 3.13 ft³ of mortar per 100 ft² of wall for a ⅜ in joint.

The Brick Calculator assumes a single wythe in running bond. For a double-wythe wall, run it once per wythe.

Mortar is a separate, smaller-volume calculation

Mortar fills the joints between bricks, not the bricks themselves, so it's estimated separately from the brick count. The amount depends on the brick size, the joint thickness and the bond pattern. BIA's figures are net quantities based on the theoretical joint dimensions, so the waste allowance goes on top. BIA calls the masons' rule of thumb — eight bags of masonry cement per 1,000 modular brick — a very rough estimate that includes an unspecified amount of waste. Bag yield varies by product, so use the yield given for the mix you buy.

The Mortar Calculator turns a brick or block count into mortar volume and bags. For what mortar is made of, and how it differs from concrete and grout, see Concrete vs Cement: What's the Difference?.

Concrete block (CMU) walls

Concrete block walls are estimated separately from brick. The block count uses the same area method with the block's face size instead: a standard 8 × 16 in block, including its mortar joint, covers 8/9 ft² of wall, so the Concrete Block Calculator uses 1.125 blocks per square foot of net wall area before waste.

Mortar and grout are separate calculations from the block count. Mortar bonds the blocks together; for conventional hollow blocks it is usually laid on the face shells only, so block mortar is not estimated the same way as brick mortar. Grout fills the block cells that contain reinforcement and is needed only where the design calls for it. The Block Wall Calculator estimates blocks, mortar and grout together, and the Concrete Block Fill Calculator estimates grout only.