Mortar Calculator

Brick takes more mortar than block

Mortar fills the joints, and a brick wall has far more joints per square foot than a block wall. A square foot of modular brick holds 6.75 bricks, while the same area of block holds just over one unit.

That is why 100 sq ft of brick needs about 10 bags of 80 lb mortar, but 100 sq ft of block needs about 8. Pick the right unit before you trust the number.

How we work it out

For brick, we count the bricks in the wall, then use about 8.1 cu ft of mortar per 1,000 bricks with 3/8 in joints. An 80 lb bag of premixed mortar makes about 0.66 cu ft.

For block, we use about 6.25 bags per 100 blocks. Both methods assume standard joint size; wider joints or a lot of rework will use more.

Where mortar gets wasted

• Droppings at the base of the wall and on the scaffold.
• Batches that stiffen before you use them, especially in hot or windy weather.
• Extra joint fill at corners, sills and around openings.
• Learning the trowel: first-timers drop more than a mason does.

Mix small batches

Mortar has a limited working time once water is added. Mix only what you can lay before it starts to stiffen, often a bag at a time for one person. That habit also keeps the waste close to the 10% default.

Mortar is sold in types that differ in strength. Which type a wall needs is set by the job and local code, so check before buying.

Get the unit count first

If you have not counted units yet, start with the brick calculator or the concrete block calculator. Both also give a mortar estimate, so you can check one number against the other.