Mortar Calculator
Accurate mortar estimation prevents costly job-site delays. This calculator determines the number of 80-lb mortar bags needed for brick and concrete block (CMU) projects based on wall area, masonry unit type, and joint thickness, with an adjustable waste factor.
Mortar requirements depend on the masonry unit size and joint thickness. Standard modular bricks (3.5" x 2.25" x 8") require about 3.5 cubic feet of mortar per 100 square feet of wall with 3/8-inch joints. Concrete masonry units (CMU blocks) use less mortar per square foot because fewer joints are needed for the same wall area.
Each 80-lb bag of pre-mixed mortar yields approximately 0.5 cubic feet when mixed. This calculator uses industry-standard coverage rates from the Brick Industry Association (BIA) and adjusts proportionally for non-standard joint thicknesses.
The waste factor (default 10%) accounts for mortar that falls during application, mortar left in the mixer, and mortar that sets before use. For experienced masons, 5-8% waste is typical. For DIY projects, consider 15% waste. In cold weather, mortar sets faster and waste increases. Plan for 12-15% in temperatures below 40°F.