Mortar Calculator
Mortar holds masonry units (bricks, blocks, or stone) together and fills the joints between them. Calculating the right amount of mortar before starting a project avoids running out mid-job and prevents the cost and quality issues of mixing mortar in small batches. The amount of mortar depends on the number of masonry units, the joint thickness, and the size of the units. Standard brick laid with a 3/8-inch joint typically requires one 60-lb bag of mortar mix for approximately 30 to 40 bricks. Concrete masonry units (CMU blocks) are larger but have hollow cores, so coverage varies. This calculator provides an estimate based on the number of units and the mortar joint thickness. The waste factor (default 20 percent) accounts for mortar squeezed out during laying, dropped material, and mixing losses. For a more precise estimate, consult the Brick Industry Association (BIA) technical notes or the National Concrete Masonry Association (NCMA) recommendations for your specific unit size.
Mortar bag estimate formula
Coverage rates are scaled from the standard 3/8-inch joint. Thicker joints use more mortar proportionally.
Joint scale = Joint thickness (in) / 0.375
Units per bag = Base units per bag / Joint scale
Base bags = Ceiling(Units / Units per bag)
Total bags = Ceiling(Base bags x (1 + Waste %))
Base units per 60-lb bag at standard joint: brick 35, CMU 8x16 = 8, CMU 12x16 = 6.
Frequently asked questions
How many bricks does one bag of mortar cover?
A 60-lb bag of mortar mix typically covers about 30 to 40 standard bricks at a 3/8-inch joint thickness. A 80-lb bag covers about 40 to 55 bricks. Coverage varies with joint thickness, brick size, and mortar waste. This calculator uses 35 bricks per 60-lb bag as a conservative estimate.
What is the standard mortar joint thickness for brick?
The standard mortar joint for brick masonry is 3/8 inch (0.375 in), per the Brick Industry Association (BIA) Technical Note 10. This applies to both the bed joints (horizontal) and head joints (vertical). Thicker joints use more mortar per unit.
What type of mortar should I use for brick and block?
Type S mortar (1 part portland cement, 0.5 part lime, 4.5 parts sand) is recommended for below-grade masonry, exterior walls, and areas exposed to freeze-thaw cycles. Type N mortar is suitable for above-grade exterior and interior walls. For retaining walls, use Type S. Check your local building code.
How much mortar do I need for concrete blocks (CMU)?
Standard concrete masonry units (CMU) use more mortar than brick because of their larger face shells and cross-webs. A single 8x8x16 CMU requires approximately 0.03 to 0.04 cubic feet of mortar (about 1/28 of a cubic foot). This calculator adjusts the coverage estimate based on the unit type.
Should I add extra mortar for waste?
Yes. Mortar waste from mixing, droppings, and over-application typically adds 20 to 30 percent to the theoretical requirement. This calculator includes a user-adjustable waste factor, defaulting to 20 percent.
Sources
- Brick Industry Association: Technical Note 10 - Mortar for Brick Masonry.
- National Concrete Masonry Association (NCMA): Mortar and grout data.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. Coverage rates are estimates. Verify with product label.