How Many Bricks or Blocks Does One Bag of Mortar Lay?

One 80 lb (36 kg) bag of pre-blended mortar lays roughly 35 to 37 standard bricks, or 12 to 13 standard 8 in (200 mm) concrete blocks. A 60 lb (27 kg) bag lays about 26 to 28 bricks or 9 to 10 blocks. Those are the coverage figures QUIKRETE and SAKRETE publish for their bagged mortars, laid with 3/8 in (9.5 mm) joints.

Assumptions behind those numbers: standard brick (3 5/8 in by 2 1/4 in by 8 in), standard 8 in by 8 in by 16 in concrete block, 3/8 in (9.5 mm) bed and head joints, single-wythe wall, and a normal amount of site waste already included.

There is no universal bag yield, so treat any single figure as a starting point. The rest of this guide gives the coverage tables for common order sizes, shows the volume method the numbers come from, and explains why a bag lays fewer bricks than the joint geometry alone suggests.

The short answer in table form

Both figures below are published by the manufacturer for their own product, and both assume 3/8 in (9.5 mm) joints.

Assumptions: standard brick and standard 8 in by 8 in by 16 in block, 3/8 in (9.5 mm) joints, single wythe. The 60 lb, 25 kg and 30 kg rows are scaled by bag weight from the published 80 lb figure, not separately published by the manufacturer.

Two things are worth noticing. The two brands differ by about 6 percent, which is a fair measure of how much any coverage figure can move. And the smaller bags are pro rata, so if a data sheet for your exact bag exists, it beats the arithmetic here.

Bags per brick quantity

These are the order sizes people actually search for. The middle columns come from the manufacturer coverage figures above. The right column comes from the volume method, which is explained further down.

Assumptions: standard brick (3 5/8 in by 2 1/4 in by 8 in), 3/8 in (9.5 mm) bed and head joints, single-wythe running bond, one bed joint and one head joint per brick, no collar joint. Bag counts include the waste already built into the published coverage figures. The volume column is the net mortar that ends up in the joints, with no waste added.

The gap between the two is the point of this guide, and the section on why bags lay fewer bricks than the maths suggests explains it.

Bags per block quantity

Concrete block is a different job. Each unit covers about 0.89 sq ft (0.083 m²) of wall on its own, so one block replaces roughly six bricks and needs far fewer joints per unit of wall.

Assumptions: standard 8 in by 8 in by 16 in concrete block (actual size 15 5/8 in by 7 5/8 in by 7 5/8 in), 3/8 in (9.5 mm) joints, full mortar bedding, no waste in the volume column.

Face-shell bedding, where mortar goes on the two outer shells of a hollow block and not the cross webs, uses far less mortar than full bedding. On a net-volume basis it is roughly a third of the full-bed figure. It does not cut the bag count by anything like that much, because most of the difference between the volume and the bag count is waste rather than joint size.

Unit size changes everything

The single biggest variable is not the bag, it is the unit. Small units mean more joints per square foot of wall, and more joints mean more mortar.

Assumptions: 3/8 in (9.5 mm) bed and head joints, single wythe, full bedding, one bed joint and one head joint per unit, no collar joint and no waste. Brick dimensions are specified sizes; block dimensions are the actual sizes of nominal 4, 6, 8 and 12 in units.

A 12 in block takes more than 50 percent more mortar per unit than an 8 in block, even though both cover the same wall area. If you switch block width late in a job, the bag count moves with it. The mortar joint thickness guide covers the other half of that equation.

Joint width moves the total by a third

Joint thickness feeds into the mortar volume twice, once through the bed joint and once through the head joint, so a small change in the joint makes a large change in the order.

Assumptions: standard brick, single wythe, full bed, no waste. Brick counts change with the joint too, from 698 per 100 sq ft at 1/4 in to 616 per 100 sq ft at 1/2 in.

The default in most US masonry work is 3/8 in, and TMS 602, the masonry specification, sets that as the value to use when the drawings do not say otherwise. If your drawings call for something else, use their figure rather than the default.

Why a bag lays fewer bricks than the geometry suggests

This is the part most bag-coverage articles skip, and it is the reason two honest sources can be a factor of two apart.

Work out the mortar that physically ends up in the joints of 1,000 standard bricks and you get about 8.4 cu ft (0.24 m³). The Brick Industry Association’s Technical Note 10 puts the same figure for modular brick at 8.1 cu ft per 1,000, which is within half a percent of the same calculation, so the geometry is sound.

Then there is a units problem that catches people out. The 8.4 cu ft is wet mortar, the volume sitting in the joints. A bag holds dry material, and dry cement and sand take up roughly a third more space than the mortar they make, because the paste fills the voids between the sand grains once water is added. So 8.4 cu ft of joints needs closer to 11 cu ft of dry material before any waste at all. That is the step the brickwork mortar calculation works through in full.

Now count the mortar that leaves the mixer. A mason spreads a bed thicker than the finished joint and the brick squeezes it down. The excess is struck off, and a good share of it never goes back on the board. Head joints are buttered full and generously. Mortar dries on the board, sticks in the mixer, and drops off the scaffold. None of that shows up in a joint, and all of it comes out of a bag.

That is why the published coverage figures land where they do. QUIKRETE’s 37 bricks per 80 lb bag works out to roughly twice the net joint volume per brick. The Concrete Masonry and Hardscapes Association reaches a similar place from a different direction: one 70 lb (32 kg) bag of masonry cement lays about 30 hollow blocks, and one 94 lb (43 kg) bag of portland cement in a cement-lime mortar lays about 62.

So there are two defensible answers, and they answer different questions:

• Net joint volume tells you how much mortar the wall contains. Use it to compare units, joints and designs, and to check that an estimate is sane.
• Published bag coverage tells you how many bags to buy. It already carries the waste.

The Brick Industry Association’s own advice sits between them: add 15 to 25 percent to a calculated mortar quantity for waste, and at least 5 percent to a brick quantity for breakage. A careful mason on a clean, repetitive job will land near the low end of that. A first-timer laying brick on a windy day will burn through more than the bag figure suggests.

A worked example

A single-wythe garden wall, 20 ft long and 6 ft high, in standard brick with 3/8 in joints.

Wall face area = length × height
Number of bricks = area × bricks per sq ft
Net mortar = bricks × net mortar per brick
Bags = bricks ÷ published coverage per bag

1. Wall face area = 20 ft × 6 ft = 120 sq ft (11.15 m²)
2. Bricks = 120 sq ft × 6.55 per sq ft = 786 bricks
3. Add 5 percent for breakage = 826 bricks to order
4. Net mortar = 786 × 0.00836 cu ft = 6.6 cu ft (187 L)
5. Net mortar plus 20 percent waste = 7.9 cu ft (224 L)
6. Bags by coverage figure = 786 ÷ 37 = 21.2, so 22 bags of 80 lb (or 786 ÷ 27.75 = 28.3, so 29 bags of 60 lb)

Step 5 and step 6 do not match, and they are not meant to. Step 5 is the mortar that will be in the wall plus a normal waste allowance. Step 6 is what the bag manufacturer says to buy. On a 120 sq ft wall the difference is a few bags, and mortar keeps indefinitely in a dry bag, so buying to the higher number costs little.

For your own wall dimensions, joint thickness and unit size, run the numbers in the Mortar Calculator rather than scaling the example above. It works the volume both ways and gives you the cement, lime and sand split if you are mixing on site.

Buying bags versus mixing on site

Bagged mortar is a blend of masonry cement and graded sand, so a bag is the whole mix apart from water. QUIKRETE Mortar Mix is formulated as ASTM C270 Type N, and QUIKRETE Mason Mix and SAKRETE Type S Mortar Mix are Type S. That choice matters more than the bag size, and the Type N versus Type S comparison covers when each one belongs on a wall.

Mixing from raw materials changes the arithmetic completely, because the yield then depends on your sand rather than a bag. As a rough guide for a Type N mix at 1 part cement, 1 part lime and 6 parts sand, sand makes up six of the eight parts, so a mortar volume of 8 cu ft needs about 6 cu ft of sand, 1 cu ft of cement and 1 cu ft of hydrated lime. The step-by-step mixing guide covers the method itself.

Common mistakes with bag counts

Treating one figure as universal. Coverage varies by product, formulation and bag weight. A figure from one brand’s Type S mortar does not transfer to another brand’s Type N.

Using nominal brick sizes in a volume calculation. A nominal 4 in brick is 3 5/8 in wide. Using 4 in inflates the mortar volume by about 10 percent. The distinction between nominal, specified and actual dimensions is set out in BIA Technical Note 10.

Forgetting that block width changes the mortar and not the count. You get 1.125 blocks per square foot whether the block is 4 in or 12 in wide, but the mortar per block nearly triples across that range.

Adding waste on top of a bag-coverage figure. The waste is already in there. Doubling up leads to pallets of mortar sitting in a garage.

Ignoring the collar joint. A two-wythe wall with a filled vertical joint between the wythes needs roughly 3.1 cu ft more mortar per 100 sq ft at a 3/8 in collar joint. Single-wythe figures do not cover it.

Where to go from here

If you are estimating by wall area rather than by unit count, the figures per square metre and per square foot are in the mortar per m² guide. If you want to see the arithmetic in full, including the cement and sand split, work through the brickwork mortar calculation.

And if your joints are anything other than 3/8 in, settle that first. It moves the total more than any other single decision on the list.