Mortar Calculator

The short answer

Roughly one cubic yard of mortar is needed per thousand modular bricks, and an 80-pound bag of mortar mix yields about 0.6 cubic feet and lays around 30 to 40 bricks. A 100 square foot single-wythe brick wall needs about 700 bricks, so about 18 to 23 bags of mix, or about a quarter of a yard if you are mixing from bulk sand and cement.

What it depends on

Joint thickness and joint profile change the volume: a tooled or raked joint uses more than a flush one, and a struck joint uses less. Mortar type is a specification decision, not a quantity one — Type N is common for above-grade general work and Type S for below grade and retaining walls, and the wrong type in the wrong place fails. Waste from dropping and tooling typically runs 10% or more.

Where this stops being useful

This is a quantity estimate. Mortar specification, reinforcement, movement joints, weatherproofing and structural capacity are engineering and code questions, and masonry work usually requires permits and inspection. A qualified mason or structural engineer should specify anything structural. General information and planning only, not engineering, structural or code advice.

Mortar and grout are different products for different jobs, and using one where the other belongs causes the joint to crack or crumble. Mortar beds bricks or blocks; grout fills the joints after tiles are set. The ratio of sand to cement differs between them, and the standard packaged products get this right already. Coverage per bag assumes a specific joint thickness and a specific mortar depth, and both vary with how much you actually bed.

Mortar is mixed in small batches and used quickly, so the order figure matters mainly for having enough bags on site rather than for buying a precise volume. The bag states a yield per bag for a standard joint and that figure is reliable for planning.

Order mortar for the joints rather than for the wall area — the volume of mortar used is a fraction of the brickwork volume. Work out the number of bricks from the wall area and the brick's face dimensions, then use the mortar yield per brick from the bag. Mixing on site in small batches gives you better control of consistency than mixing one large batch early, because mortar starts to lose workability within an hour. In hot weather, smaller batches and a damp working surface will help.

Mortar is the glue of a masonry wall, and its quantity follows the number of joints rather than the wall area directly. Every brick or block laid needs a bed underneath and a joint at one end, so the mortar consumed is roughly proportional to the number of units — which is why small units and wide joints use much more mortar than large blocks with tight joints. The working figure for a standard brick is about two hundredths of a cubic foot of mortar per unit, and for larger blocks rather more because the bed and joint are wider. Multiplying units by that figure gives the wet volume, but the dry mix you buy is bulkier than the wet mortar it makes, so bags are estimated by yield rather than by matching volumes. A typical eighty-pound bag of mortar mix yields around two-thirds of a cubic foot of mortar. Waste is larger here than in most building estimates. Mortar is mixed in batches, and any batch left unused at the end of a session sets hard and is thrown away. It is also lost to the board, the trowel and the joints that are struck and brushed. An allowance of ten per cent is a sensible minimum; on small jobs where you cannot mix an exact batch, it can be higher still. This calculator turns your wall area into a unit count, then into mortar volume and bags of dry mix. It assumes brick-sized units unless you change the units-per-square-foot figure, and a single skin of wall. The mix ratio also matters for strength and weather resistance, so follow the specification for your project rather than improvising, and check the yield printed on the bag you buy.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.