Mortar Calculator

How to Use the Mortar Calculator

Brick vs. Block: Why the Mortar Math Is Different

Brick and concrete block share a job — both need a mortar bed and head joint between every unit — but they don't share a coverage rate, because they're different sizes doing different structural work. A standard US modular brick has a nominal size of 4 × 2⅔ × 8 in., and the Brick Industry Association's Technical Note 10 (the masonry trade's own reference for estimating brick and mortar quantities) lists 6.75 bricks per square foot of net wall area for that size, laid in running bond with a standard 3/8 in. joint. That's the same coverage rate this site's brick calculator uses, and it's what this calculator uses too whenever you're in Brick mode.

A standard concrete masonry unit (CMU) is much bigger — a nominal 8 × 8 × 16 in. block, with an actual face area of 8 in. × 16 in. = 128 sq in., or 0.888 sq ft once you divide by 144 sq in. per square foot. Invert that and you get roughly 1.125 blocks per square foot of wall (1 ÷ 0.888), a straightforward geometry result rather than a published industry table, since a block's face area is a fixed, known quantity. Fewer, bigger units means fewer mortar joints per square foot of wall — which is exactly why block mortar consumption per bag looks so different from brick's.

How Many Blocks or Bricks Does a Bag of Mortar Cover?

For brick, the masonry trade's commonly used rule of thumb is about 8 bags of 80 lb pre-mixed mortar per 1,000 modular bricks laid with a standard 3/8 in. joint — the same figure the Brick Industry Association cites and the one already used on this site's brick calculator. For block, QUIKRETE's own Mortar Mix (No. 1102) product data sheet states that an 80 lb bag covers up to 12 standard 8 × 8 × 16 in. concrete blocks. Both figures assume standard joint thickness and typical mixing loss — a wider joint, a rougher block face, or more spillage during laying will all pull actual coverage down from the published number, so treat either figure as a solid planning estimate to round up from, not an exact order quantity.

Mortar type (Type N, S, M, or O) changes the mix's compressive strength and workability, not how many blocks or bricks an 80 lb bag covers — the yield figures above hold across all four ASTM C270 types when premixed in a standard 80 lb bag, so switching the dropdown below changes what mortar you should buy, not the bag count this calculator returns.

Choosing the Right ASTM C270 Mortar Type

ASTM C270, the masonry industry's governing specification for mortar, defines four mortar types by their minimum 28-day compressive strength, from strongest to weakest: M, S, N, and O. Strength isn't automatically "better" — a higher-strength mortar is also stiffer and less able to accommodate the small amount of movement every masonry wall experiences, so using an unnecessarily strong mix can actually make a wall more prone to cracking than a properly matched one. Type N, the general-purpose default this calculator starts on, is the right call for most above-grade residential brick and block walls.

If your project is structural, load-bearing, or below grade, don't guess — confirm the required mortar type with a structural engineer or your local building code before ordering. Type M and Type S are common on retaining walls and foundations for exactly that reason, and using a weaker type than the design calls for isn't something a finished wall will forgive.

Why a Waste Factor Matters

No real mortar job uses exactly the calculated quantity. Some mortar is lost to mixing waste, some squeezes out of the joint during laying and gets scraped off, and small measurement errors compound across a whole wall. 10% is a commonly cited waste allowance for masonry materials, matching the default already used on this site's brick calculator and paving calculator. This calculator defaults to that same 10%, but you can dial it down for a simple, well-planned wall once you're confident in your own mixing and laying accuracy, or raise it for a first attempt or a wall with lots of cuts and corners.

Mortar Needed by Wall Area

For a quick planning reference before you measure your own wall precisely, here's how brick and block mortar bag counts scale across common wall areas, using each material's own coverage rate above and this calculator's 10% default waste factor.

Notice how far fewer bags block walls need for the same wall area — fewer, bigger units mean fewer joints, which is the whole reason block construction goes up faster than brick for a comparable footprint.

Buying Bagged Mortar Mix

An 80 lb bag of pre-mixed mortar (Type N or Type S) typically runs about $8 to $12 at major US home-improvement retailers as of 2026, with premium or specialty blends costing more. That's material cost only — it doesn't cover the brick or block itself, sand for bedding, or labor. Buying by the pallet (commonly 42 bags per pallet) from a masonry supplier is usually cheaper per bag than single-bag retail pricing once a job climbs past a couple dozen bags, which is worth asking about before a large order.

Once you've worked out your mortar needs, it's worth planning the rest of a masonry project too. If you haven't settled on brick quantities yet, our brick calculator works out both bricks and mortar together from wall dimensions. Most brick and block walls also need a poured concrete footing beneath them — our concrete calculator works out the cubic yards needed by length, width, and thickness. If your project extends to a tiled surface, our tile calculator covers tile count, thin-set mortar, and grout the same way this tool covers brick and block mortar, and for an adjoining paver patio or walkway, our paving calculator handles paver count and bedding sand. If the exterior walls above your masonry need a finish coat, our new stucco calculator works out bags by wall area, and if the same project includes a new roof, our new roofing calculator works out shingle bundles from roof dimensions and pitch. Browse every tool in this category on our renovation calculators hub.