Mortar Calculator
Calculate mortar needed for bricklaying, block walls, and stone work. Enter wall dimensions for accurate bag counts.
Required Materials
How this calculator works
The mortar volume is determined by multiplying the total wall area by the mortar joint thickness, adjusted for the specific masonry unit's coverage factor. This yields the total cubic volume of wet mortar required, which is then divided by the yield per bag (accounting for waste and mixing conversion) to estimate the total bag count. Formula based on TMS 402/602 (Masonry Standards Joint Committee) and ASTM C270.
How to Calculate Mortar Requirements
Estimating masonry mortar accurately is essential to prevent project delays while minimizing costly material waste. The foundational calculation requires knowing the total square footage of the wall surface, the specified thickness of the mortar joints (typically 3/8 inch for standard brick and block), and a coverage factor dictated by the masonry unit type. Standard bricks require more mortar per square foot than large concrete masonry units (CMUs) because of the higher joint-to-unit ratio.
To perform the math manually, multiply the square footage by the joint thickness in inches, then divide by 12 to convert to cubic feet. Next, apply the masonry type multiplier to account for bed and head joints. Finally, divide the total cubic footage of wet mortar by the yield of a standard pre-blended bag (an 80-lb bag yields approximately 0.6 to 0.7 cubic feet of mixed mortar) and add a 5% to 10% contingency factor for jobsite waste and spillage.
What Affects Mortar Consumption?
Several jobsite variables significantly influence the exact volume of mortar consumed during construction. Joint thickness is the most critical factor; even a tiny deviation from a 3/8-inch joint to a 1/2-inch joint can increase total mortar consumption by over 25 percent across a large commercial or residential wall assembly.
Unit size, shape irregularities, and masonry absorption rates also alter mortar usage. Irregular natural stone requires variable backing beds and extensive chinking, drastically increasing mortar demands compared to uniform extruded clay bricks or precision-manufactured concrete blocks. Additionally, extremely dry bricks or blocks can suction moisture out of the mortar too quickly, forcing masons to use more mud to achieve proper bond strength and joint tooling consistency.
Frequently Asked Questions
How many 80-lb bags of mortar are in a cubic yard?
There are approximately 40 to 42 eighty-pound bags of pre-mixed mortar in a single cubic yard of wet mixed mortar, depending on the exact water-to-mix ratio and dry bulk density.
Should I add extra bags for waste?
Yes, it is standard industry practice to add a 5% to 10% waste factor to your final bag count to account for dropped mortar, cleanup waste, and minor calculation variances.
Can I reuse leftover mixed mortar?
No, mortar begins the hydration and setting process shortly after mixing with water. Retempering mortar that has begun to stiffen beyond initial set compromises its compressive and bond strength.