Mortar Calculator
Calculate the number of bricks or blocks needed for your wall and work out exactly how many bags of mortar you need to buy.
Define your wall and materials
Enter the wall area, pick your masonry type, and select how you plan to mix the mortar to get an accurate material estimate.
How to Calculate Mortar for a Wall
Calculating mortar relies on geometric deduction. Instead of trying to calculate the complex web of mortar joints, we look at the big picture: the total volume of the wall minus the total volume of the bricks.
A mortar calculator determines how much mortar is needed for brick, block, or stone masonry. Enter the wall dimensions, masonry unit size, and mortar joint thickness to calculate the required volume. Mortar requirements vary by unit dimensions and joint size. Add 5–10% extra mortar to account for waste and spillage.
A mortar calculator determines how many bricks or blocks you need by finding the face area of one brick (including its mortar joint) and dividing the total wall area by it. Once the brick count is known, we multiply it by the physical volume of a single brick. Subtracting this "brick volume" from the overall "wall volume" reveals the exact cubic volume of mortar required.
The surface area of one brick plus one bed joint and one head joint is (L + J) × (H + J). Dividing your wall area by this gives the exact number of bricks needed.
Mortar falls on the ground, gets stuck in the mixer, and fills holes inside extruded bricks. A 10% to 15% wastage allowance is non-negotiable for masonry work.
Important: This calculator assumes a "single wythe" wall (one brick thick). If you are building a double-brick structural wall, simply double the total materials output.
Mix Types
Type N vs. Type S Mortar
Not all mortar is the same. The ratio of Portland cement, lime, and sand dictates the strength, flexibility, and bonding properties of the mix.
Type N (Normal)
Medium strength (750 psi). Best for general-purpose above-grade walls, brick veneers, and interior walls. Highly workable and flexible.
Type S (Strong)
High strength (1800 psi). Ideal for below-grade applications, foundations, retaining walls, and areas subject to wind or seismic loads.
Type M (Maximum)
Highest strength (2500 psi). Used for heavy loads, driveways, and severe frost-exposed masonry. Less workable than N or S.
Rule of Thumb: Stronger is not always better. Mortar should ideally be slightly weaker than the masonry units it bonds so that under stress, the easily-repairable mortar cracks before the brick snaps.
Important Considerations
Frogs, Cores, and Wasted Material
Bricks with holes
Many modern extruded bricks feature 3 to 10 holes (cores) through the middle. While laying, mortar squeezes into these holes, consuming significantly more material than a solid brick. If laying cored bricks, push your wastage allowance to 15% or 20%.
Site-Mixed Ratios
If mixing on-site with bulk materials, a common ratio is 1 part Portland cement, 1 part hydrated lime, and 6 parts masonry sand (for Type N), or roughly 1 part masonry cement to 3-4 parts sand. Wetting the mix shrinks the dry volume by roughly 25-30%.
Weatherproofing
Choosing the Right Mortar Joint Profile
The shape of the mortar joint isn't just about aesthetics; it dictates how well the wall sheds water. Water ingress is the leading cause of masonry failure, especially in freeze-thaw climates.
Highly Weather-Resistant
- Concave Joint: Created with a curved jointer tool. It compresses the mortar against both bricks, sealing the edge and shedding water perfectly. The industry standard for exterior walls.
- V-Joint: Similar to concave but uses a V-shaped tool. Offers excellent water shedding and sharp shadow lines.
- Weather-Struck: Sloped downwards and outwards. Sheds water well but requires more skill to strike cleanly.
Poor for Exterior Weathering
- Raked Joint: Mortar is scraped back to leave a deep shadow. Beautiful, but creates a shelf where water and snow sit, accelerating deterioration.
- Flush Joint: Mortar is cut off flat with the trowel. It doesn't compress the mortar to seal the microscopic gaps at the brick edge. Best reserved for walls that will be painted or rendered.
The Hidden Trap of "Sand Bulking"
If you are mixing your own mortar on-site using the classic 1:4 ratio (one part cement to four parts sand), you must account for moisture in the sand. Bone-dry sand and fully saturated sand occupy roughly the same volume. However, slightly damp sand—which is how it is usually delivered—undergoes "bulking."
Surface tension pushes the damp sand particles apart, causing the pile to expand in volume by up to 25% to 30%. If you measure four buckets of damp sand, you are actually only getting about three buckets worth of actual sand. This results in a mortar mix that is far too rich in cement, leading to severe shrinkage cracks as it cures. To compensate for damp sand, an on-site 1:4 mix should often be measured closer to 1:5 by volume.
Curing Conditions
Temperature Limits for Bricklaying
Mortar does not dry; it cures through a chemical reaction called hydration, which requires moisture and specific temperature ranges to achieve full strength.
Cold Weather (Below 40°F / 4°C)
If the water in the mortar freezes before it cures, the expansion of the ice will destroy the bond, turning the mortar to dust. If laying in cold weather, bricks must be covered, and the mortar materials (sand and water) should be heated. Never lay bricks on frozen foundations.
Hot Weather (Above 90°F / 32°C)
High heat and wind cause the water in the mortar to evaporate before hydration can finish. This results in weak, crumbly joints. In hot weather, bricks should be lightly dampened before laying (so they don't suck moisture from the mortar instantly), and the finished wall may need to be misted with water and covered with plastic to retain humidity.
Frequently Asked Questions
How do you calculate mortar for a brick wall?
To calculate mortar for any brickwork or blockwork, you first need to determine the total volume of your wall. You do this by multiplying the length, height, and thickness (or width) to find the overall area and volume. Next, calculate the volume of the bricks or blocks themselves (such as a standard CMU). Subtract the masonry unit volume from the overall wall volume. This leaves you with the exact quantity of mortar needed to fill every bed joint (the horizontal layer below a course) and head joint (the vertical gap). Our calculator handles this geometry for you. Always remember to add 10% to 15% for waste to ensure you don't run out of material on site.
How many bags of mortar do I need for 1000 bricks?
As a general rule of thumb in construction, it takes about 14 to 16 standard 80 lb bags of pre-mixed mortar to lay 1,000 standard modular bricks with a 3/8-inch mortar joint. You just add water to these bags. If you are mixing it yourself on-site at a standard ratio (like 1:4), a mason will typically need about 5 to 6 bags of Portland cement (94 lb) and roughly one cubic yard of mason's sand.
Should I use Type N or Type S mortar?
Type N mortar is a versatile, medium-compressive-strength mix suitable for general-purpose exterior and interior above-grade walls (like brick veneers). Type S is a higher-strength mix designed for below-grade applications, heavy load-bearing structures, a retaining wall, masonry foundations, and areas subjected to high wind or seismic loads.
Do frogs and cores in bricks use more mortar?
Yes. Bricks with 'frogs' (indentations on top) or 'cores' (extrusion holes through the middle) require more mortar to lay because the wet mixture fills these voids. While a standard geometric calculator provides an accurate baseline for solid units, you should increase your allowance for waste by an additional 5% to 10% if you are laying heavily cored bricks to ensure you have enough bagged mix or raw materials.
How many bricks are in a square metre or square foot?
Estimating coverage depends on the physical dimensions of the unit and the joint. Using standard modular bricks (roughly 8" × 2.25" face) with a 3/8" joint, you need about 7 bricks per square foot of wall area. In metric, using standard UK/Aus bricks (215mm × 65mm face) with a 10mm joint, you need exactly 60 bricks per square metre for a single-skin wall.
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Disclaimer
This calculator estimates material quantities assuming mathematically perfect brick laying. It calculates the theoretical geometric volume of joints based on your inputs and does not account for mortar pushed into the cavities of cored bricks or excessively thick joints.
Pack yields and material densities vary significantly between manufacturers and sand types. Mix ratios on-site are subject to human error and bulking of damp sand. Always rely on the coverage figures printed on the bags you purchase, and add a sufficient wastage allowance (typically 10-15%) to ensure you do not run out of material mid-job.
Furthermore, this tool is intended solely for volume estimation and material planning purposes. It does not replace professional structural engineering or masonry advice. Always consult local building codes and a qualified professional to ensure your wall assembly meets the required structural and load-bearing standards for your region.
Last updated
Formulas, brick dimensions, and layout checked on this date.