Mixing Block and Brick in One Wall: Why the Bag Count Isn't in the Data Sheet

Updated: 9/5/2026

A wall of all standard concrete block needs a certain number of mortar bags. A wall of all standard bricks needs a different number. But what about a wall that uses both — say, a decorative pattern that alternates block and brick, or a repair that mixes what was already there with new units? The mortar bag calculator handles this by adding the block and brick together before rounding up to a whole bag count. That is a deliberate assumption the calculator makes, not something the manufacturer guarantees — and understanding where it comes from, and where it might not hold, matters if you want to know whether you are buying the right number of bags.

What the data sheet actually says

QUIKRETE Masonry Cement, data sheet (retrieved 2026-09-04), states exactly:

“A typical mix design consisting of one bag of Masonry Cement and 240 pounds of QUIKRETE Mason’s Sand will yield approximately 2.75 cu. ft. of mortar and will lay about 46 standard block or 144 standard bricks.”

Read that sentence closely. It says “or” — not “and”. The data sheet lists two separate statements: one bag and 240 lb of sand lay about 46 block, OR about 144 bricks. It does not say anything at all about what happens when you mix both block and brick into the same wall.

How the calculator approaches a mixed wall

With no guidance from the manufacturer, the mortar bag calculator makes its own assumption: treat the yield per bag as linearly divisible between the two unit types. In other words, one bag lays 46 block OR 144 brick, so it lays 1/46th of a bag per block and 1/144th per brick — and if you add the fractional contributions from both unit types, then round the sum up to a whole number, you get your bag count.

For a wall of 23 standard block and 72 standard bricks, that works out to:

  • Block contribution: 23 ÷ 46 = 0.5 bags
  • Brick contribution: 72 ÷ 144 = 0.5 bags
  • Sum: 0.5 + 0.5 = 1.0 bags

The result is exactly 1.0, so no rounding is needed in this case. One bag of Masonry Cement and 240 lb of Mason’s Sand will yield 1 × 2.75 = 2.75 cu. ft. of mortar, according to the data sheet.

Where the assumption might matter

The choice to add the contributions before rounding makes a difference when the sum is not a whole number. But even in this example, where the sum comes out to exactly 1.0, the assumption becomes visible if you consider an alternative: what if you treated the block and brick as two fully separate jobs, rounded each up on its own, then added the bag counts together?

In that case:

  • Block contribution alone: 23 ÷ 46 = 0.5, which rounds up to 1 bag
  • Brick contribution alone: 72 ÷ 144 = 0.5, which rounds up to 1 bag
  • Total: 1 + 1 = 2 bags

Suddenly the answer is 2 bags instead of 1 — exactly double — even though the arithmetic is identical and only the rounding order changed.

This is not a trick. The two methods represent two different assumptions about what the data sheet’s “or” actually means. The calculator’s approach — add the fractions first, then round — assumes that the yield per bag can be split smoothly between block and brick. The alternative — round each unit type to its own bag count, then add — assumes that each unit type consumes a whole number of bags before any of the other type is used, wasting the spare capacity in each bag.

When this assumption applies

If your wall contains only one unit type — all standard block, or all standard bricks — this question does not arise. The data sheet gives you 46 or 144 directly, and the calculator uses those figures. The additive assumption with the linear split only comes into play once you mix both unit types in the same wall.

Whether 1 bag or 2 bags is actually correct for your specific mixed wall is something only QUIKRETE’s own data could settle, and they have not published guidance on it. The calculator calls out the assumption because it recognizes the gap — a wall with both unit types falls between the two examples the data sheet covers. You are not making a mistake by following the calculator; you are making a deliberate choice to use the additive method when the manufacturer has not told you which method is right. For most homeowners doing a small repair or decorative pattern, the difference — if it shows up at all — is likely to be buying one or two extra bags as insurance, a small price for the lack of certainty.