Mortar Calculator

What Is a Mortar Calculator?

A mortar calculator estimates the mortar needed to lay bricks or concrete masonry blocks in a wall. Enter the wall length, height, and thickness, then enter the size of the masonry unit and the mortar joint. The calculator estimates the wall area, approximate brick or block count, mortar volume, bag count, waste allowance, and optional material cost.

The estimate is useful when you are planning a new brick wall, block wall, garden wall, garage, fireplace surround, or small masonry repair. The mortar volume is calculated from the wall's gross volume and the space left between a regular grid of masonry units. It provides a practical starting figure for a material list; the actual quantity depends on the unit shape, wall bond, joint size, openings, and how the mortar is mixed and placed.

How Much Mortar Do I Need?

Mortar quantity depends on the size of the wall, its thickness, the size of each brick or block, and the width of the joints. A larger wall needs more mortar, but unit size also matters: smaller bricks create more joints over the same wall area than large blocks. A thick wall contains more masonry and mortar than a single wythe wall. Enter the actual dimensions from your plans or measure the finished wall layout to get a useful estimate.

If you are building several walls with the same unit type and dimensions, enter their combined count as the number of walls. For walls of different heights, thicknesses, or masonry units, calculate each group separately and add the bag estimates. This prevents a large opening or a short return from distorting the dimensions of the main wall. Enter doors and windows as separate deductions when they make up a meaningful part of the wall area.

The calculator rounds the mortar bag count up to complete bags based on the yield you enter. A bag's weight is not the same as its volume yield after mixing. Check the product label or data sheet and enter the stated yield in litres or cubic feet. If you are buying ready-mix mortar by volume, use the estimated cubic feet or cubic yards to discuss the order with your supplier.

How the Mortar Volume Formula Works

The calculator treats the wall as a regular grid. First it finds the wall face area from length and height, then accounts for the number of walls and wall thickness. It estimates masonry units from a repeating face module: unit length plus joint width, multiplied by unit height plus joint width. The proportion of each module occupied by the unit is used to estimate the volume of masonry. The remaining wall volume is the estimated mortar volume.

• Wall area = wall length × wall height × number of walls
• Unit module area = (unit length + joint width) × (unit height + joint width)
• Estimated units = wall face area ÷ module area × layers through wall
• Mortar volume ≈ gross wall volume − masonry unit volume
• Order volume = mortar volume × (1 + waste allowance ÷ 100)
• Bags = round up (order volume ÷ published bag yield)

Brick Mortar Calculator

Brick walls use many small units, so their bed joints and head joints account for a noticeable share of the finished wall volume. A standard modular brick is often close to 200 millimetres long and 60 millimetres high, but brick dimensions vary by country, product, and style. Measure the brick you will use, and enter the face length, face height, and depth that match your wall construction. The calculator's default brick dimensions are only a starting example.

Brick counts depend on the bond pattern and the way corners, openings, and ends are finished. Running bond, stack bond, and other patterns arrange units differently. The estimated unit count uses a repeating rectangular grid and does not create a detailed cutting schedule. Add extra bricks for cuts and breakage using a separate allowance when preparing a full material order. The mortar estimate likewise assumes regular joint spacing rather than a detailed architectural takeoff.

Block and CMU Mortar Calculator

Concrete masonry units, often called concrete blocks or CMUs, cover more wall area per unit than standard bricks. A common nominal block is described as 8 by 8 by 16 inches, while its actual dimensions are usually smaller to leave room for mortar joints. Other block depths and face dimensions are available. Enter the actual unit dimensions, not only the nominal name, for a closer unit count and mortar estimate.

Hollow concrete blocks are not solid rectangles. Their webs and face shells leave open cores, and those cores are often empty, reinforced, or filled with a separate masonry grout. The mortar calculator estimates the bedding and head-joint space around the outside dimensions of the block. It does not calculate grout for hollow cores. Use a core-fill grout estimate for that separate material, and follow the structural drawings to determine which cells should be filled.

Mortar Joint Width and Bed Joints

A mortar joint is the layer between neighbouring units. The horizontal joint under a course is called a bed joint, and the vertical joint between the ends of units is a head joint. Both joint directions affect how much mortar a wall uses. Wider joints increase the empty part of the repeating module, which increases the estimated mortar volume. A small change in joint size can add up across many courses and units.

Use the joint width specified for the masonry unit and the project's plans. Do not make joints wider just to use up material or to compensate for inconsistent units. The permitted joint dimensions depend on the unit, masonry system, workmanship requirements, and local building rules. If the finished wall will be exposed, consistent joints also affect the appearance of the bond and the visible lines between bricks or blocks.

Wall Thickness, Bond, and Multiple Layers

Wall thickness is important because mortar fills joints through the depth of the wall, not only across its front face. A single wythe of brick has a different thickness from a multi-wythe wall or a block wall. Enter the full wall thickness and the depth of one masonry unit. The calculator uses their ratio to estimate how many unit layers run through the wall.

This is a volume estimate rather than a bond design. Real multi-wythe walls may use headers, ties, cavities, reinforcing, or different unit arrangements. Those details can change the quantity of masonry and mortar. For veneer walls, do not include the backing wall unless it will also be built from the same masonry units. For cavity walls, calculate each masonry leaf separately and account for the cavity as its own space.

Subtract Openings and Add Separate Wall Sections

Large doors, windows, garage openings, and passageways reduce the amount of wall that needs masonry and mortar. For a more accurate estimate, subtract each opening's width multiplied by height from the wall area before using the calculator, or calculate the remaining wall sections separately. Small openings may be covered by a normal material allowance, but large openings should not be counted as solid masonry.

Walls with many corners, piers, pilasters, returns, or steps take extra time and can use more material than a plain rectangular face. You can estimate each simple wall segment separately, then add the mortar and unit totals. Keep a short written takeoff of the wall lengths and heights. That makes it easier to check the total area and catch a missing return or a double-counted section before ordering bags.

Bag Yield, Mortar Mix, and Material Cost

Bagged mortar products can have different yields because bag size and mix formulation vary. The yield is the approximate volume of usable mortar made after mixing, as stated by the manufacturer. Enter this yield rather than dividing by the dry bag weight. If the package lists coverage per number of bricks or blocks instead of volume, compare that coverage with the estimated unit count and use the product information for the final order.

The optional cost estimate multiplies the number of whole bags by your price per bag. It does not include delivery, tools, labor, taxes, mixer rental, or other masonry materials. If you buy different mortar types for different sections, calculate them separately. Keep the product type and colour consistent where a uniform visible finish matters, and check that the selected mortar is suitable for the unit and application.

Add a Practical Waste Allowance

A waste allowance covers mortar left in the mixing tub, spillage, dropped mortar, small variations in joint thickness, and differences between the measured wall and the finished layout. The default percentage is an initial planning value. The appropriate allowance depends on the crew's experience, wall complexity, unit shape, site access, weather, mixing method, and whether the wall has many corners or openings.

The calculator adds waste after estimating the base mortar volume and before rounding up to full bags. If your supplier's coverage table already includes a waste factor, avoid adding the same allowance twice. For a repair using a small amount of mortar, a full bag may be the smallest practical purchase even if the estimated amount is much lower. Mixed mortar has a limited working time and should not be saved for another day unless the manufacturer explicitly allows it.

Worked Example for a Brick Wall

Consider a single wall that is 5 metres long, 2.4 metres high, and 100 millimetres thick. Suppose it uses bricks measuring 200 millimetres long, 60 millimetres high, and 100 millimetres deep, with 10 millimetre joints. The wall face is 12 square metres. The repeating unit module is 210 by 70 millimetres, so the calculator estimates the number of brick positions and the volume occupied by the units.

The remaining volume in the wall envelope is the approximate mortar volume. If a 10 percent waste allowance is selected, that extra is added to the base estimate. The final quantity is divided by the bag yield entered from the product label and rounded up to complete bags. The example demonstrates the process; actual brick dimensions, openings, bond pattern, workmanship, and mix yield can change the order quantity.

Common Mortar Estimating Mistakes

Small input errors can cause a large difference when they are repeated across a whole wall. Check that all dimensions use the displayed unit system, and distinguish unit depth from wall thickness. Measure the masonry unit itself rather than its nominal catalogue size. Remember that the calculator estimates mortar joints and unit count; it does not include grout for hollow block cores or concrete for a footing.

• Entering nominal block dimensions instead of the actual face and depth measurements.
• Leaving wall thickness equal to one unit depth when the wall has several layers.
• Using the joint width as a gap only in one direction when both bed and head joints are present.
• Forgetting to subtract large doors, windows, or other openings from wall area.
• Using a bag's dry weight instead of its published mixed mortar yield.
• Assuming block core fill, reinforcement, ties, or cavity fill is included in the mortar estimate.
• Ordering the exact calculated amount without considering normal job waste or minimum package sizes.

Metric and Imperial Measurements

Metric mode uses millimetres for wall, unit, and joint dimensions and litres for bag yield. Imperial mode uses inches and cubic feet for bag yield. The calculator converts these values internally to a common unit so the volume calculation remains consistent. When switching systems, the displayed dimensions and bag yield are converted to the new units. Review the converted values, especially if your source measurements are rounded fractions of an inch.

For ready-mix mortar ordered by volume, cubic feet and cubic yards are common estimating units. For bagged mortar, use the unit yield printed on the package. Cost is shown in US dollars because that is the currency used by the optional price field; enter a price per bag in dollars for the estimate to be meaningful.

Choosing Mortar for the Masonry Work

Mortar products are made for different masonry units and applications. The right selection can depend on the strength and absorption of the brick or block, exposure to weather, wall design, and local requirements. A stronger mortar is not automatically the right choice for every wall. Follow the project specification and the mortar manufacturer's data sheet for the required product and mixing directions.

This calculator estimates quantity only. It does not select a mortar type, set a structural wall thickness, or determine whether reinforcement is required. If you are repairing older masonry, matching the existing materials can be important. Ask a qualified mason or building professional to review the product choice when the wall is load-bearing, historic, exposed to harsh conditions, or part of a regulated structure.

A Note About Accuracy

The result is an estimate based on a regular masonry grid with consistent units and joints. Actual use can differ because bricks and blocks may have grooves or irregular shapes, wall bond changes the unit layout, mortar can be lost during placement, and site measurements may not match the finished work. Use product coverage data when available, add a practical waste allowance, and confirm the order with your supplier or mason for a large project.