Chimney Brick Count Calculator
Count the bricks for a chimney from its width, depth and height, plus mortar bags — for a hollow rectangular stack.
How it works
perimeter = 2 × (width + depth) ÷ 12 · face area = perimeter × height · bricks = face area × bricks per sq ft × 1.05 · mortar bags = bricks ÷ 125
A chimney is a hollow rectangular column, so its brick face is the perimeter of the stack multiplied by its height. Width and depth are outside dimensions in inches, converted to feet for the perimeter. Multiplying the face area by the bricks-per-square-foot figure — about 6.9 for standard modular brick including the mortar joints — gives the brick count, then a 5% allowance covers cuts and breakage. A 70-pound bag of mortar lays roughly 125 modular bricks.
Worked example
A 24 × 16 in chimney 12 ft tall: perimeter = 2 × (24 + 16) ÷ 12 = 6.67 ft, face area = 6.67 × 12 = 80 sq ft. Bricks: 80 × 6.9 × 1.05 ≈ 580. Mortar: 580 ÷ 125 ≈ 5 bags.
Frequently asked questions
How many bricks are in a square foot?
About 6.9 modular bricks per square foot of face including the 3/8-inch mortar joints; standard and other sizes differ slightly. Multiply the chimney’s face area by that figure and round up.
Does this count the flue liner?
No — this estimates the exterior brick shell only. The flue liner, crown, cap and any firebox brick are separate items sized to the appliance and to code, so plan those independently.
How much mortar will I need?
Roughly one 70-pound bag of mortar mix per 125 modular bricks, so about a bag for every square yard or two of wall. Cold or fast-drying conditions and full joints push usage up, so keep a spare bag.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.