Mortar Calculator

Measure the length and height of each wall section and let the calculator find the gross area. Add doors, windows, or other openings inside their wall with a width, height, and quantity — the calculator deducts them automatically before totaling every section's net area.

A brick is close enough to a solid rectangular block that its mortar joints can be calculated geometrically: the space one brick's share of wall (its “module”) occupies, minus the brick itself, is the joint void mortar fills. A concrete block is hollow. Applying that same subtraction to a CMU wall would treat the block's open cores as if they were filled with mortar, wildly overstating the true requirement. Because the physical shape of the two materials is fundamentally different, this calculator never blends them into one formula — see the next two sections for how each one actually works.

The brick's specified length and height, plus your mortar joint, form a “face module” — the footprint one brick and its share of mortar occupy on the wall. Net wall area divided by the module area gives a calculated brick count. For each of those bricks, the calculator finds the module cell's volume (module length × module height × brick depth) and subtracts the solid brick's own volume (brick length × brick height × brick depth); the difference is the geometric mortar void for one brick. Summed across every brick, this is the theoretical/calculated joint volume — then a field-use allowance is applied to reach an order volume.

BIA Technical Note 10 (p. 11) advises adding roughly 15 to 25 percent to net mortar quantities for field use. 20% is the midpoint of that published range, matching the Brick Calculator's own existing mortar estimate — it is a reasonable starting point, not a value this calculator claims is universally correct. Adjust it for your crew, mix, and site conditions.

Concrete block mortar is never estimated as wall volume minus block volume — a hollow block's cores would be miscounted as mortar-filled space. Instead, the calculator finds a continuous block count the same way as brick (net wall area ÷ the block's nominal face module area — the nominal module already includes the mortar joint), applies your additional allowance, and stops there. Turning that block count into a bag count relies entirely on a verified manufacturer units-per-bag (or, for some products, ft³-per-bag) coverage figure, not on any independently calculated CMU mortar volume.

Published block-mortar coverage figures (bricks/blocks or ft³ per bag) already come from real product testing, and may already build in a nominal allowance for normal waste. There is no sufficiently explicit authoritative source supporting a universal additional percentage on top of that — so this calculator defaults the CMU additional allowance to 0%, fully editable, rather than assuming a figure it cannot verify. Add a project-specific contingency here only if you want one; brick's 20% default comes from a specific, citable source (BIA TN10) for a genuinely different, geometrically-derived quantity.

Manufacturers publish premixed mortar coverage in two different, non-interchangeable ways: a mixed volume yield per bag (cubic feet), or a unit coverage per bag (how many bricks or blocks one bag will lay). Some products publish only one; a few publish both. This calculator never converts one into the other — a bag count is always computed from whichever figure your selected or entered coverage actually published.

• Recommend a mortar type (Type N, S, M, or O) or mix ratio.
• Calculate cement, lime, or sand quantities for a site-mixed batch.
• Estimate grout or core fill for reinforced CMU cells.
• Model multi-wythe walls — this calculator is single-wythe only.
• Design structural capacity, reinforcement, or wall thickness.
• Include labor, delivery, taxes, or other installed costs.

Follow your project drawings, mortar specification, manufacturer instructions, and a qualified professional for all of the above — this calculator estimates mortar material quantity only.