Mortar Calculator
Calculate mortar mix needed for brick or block walls based on wall area, unit size, and joint thickness. See also our Brick Calculator, Concrete Block Calculator, and Grout Calculator.
How to Use the Mortar Calculator
Enter the total wall area in square feet (height x length, minus window and door openings). Select your masonry unit type — standard brick, modular brick, or CMU block in 8-inch or 12-inch widths. Choose the mortar joint thickness (3/8 inch is standard for most applications). The calculator determines the number of pre-mixed mortar bags needed in both 60-lb and 80-lb sizes, total mortar volume, and sand requirements for site-mixed mortar.
For accurate results, subtract the area of all openings (doors, windows, vents) from the total wall area before entering it into the calculator. A standard door opening is approximately 21 sq ft (3 ft x 7 ft) and a standard window is approximately 12 sq ft (3 ft x 4 ft). Pre-mixed mortar bags are convenient for small projects, while site-mixing with Portland cement, lime, and sand is more economical for large projects over 500 sq ft.
Mortar Mixing Best Practices
Mix mortar in a clean wheelbarrow or mortar box. Add about 3/4 of the water first, then add the dry mix gradually while mixing with a hoe. Add remaining water slowly until reaching the proper consistency. Let the mortar slake (rest) for 5 minutes, then remix briefly before use. Never add water to mortar that has begun to set — this weakens the final strength significantly.
Formula
Total Units = Wall Area x Units per sq ft
Mortar (cu ft) = (Wall Area / 100) x Mortar per 100 sq ft
Bags (60 lb) = Mortar cu ft / 0.5 cu ft per bag
Bags (80 lb) = Mortar cu ft / 0.6 cu ft per bag
Sand = Mortar cu ft x 3 (for site-mixed)
Example Calculation
Wall: 100 sq ft, standard brick, 3/8" joints
Bricks needed = 100 x 6.75 = 675 bricks
Mortar volume = (100/100) x 4.5 = 4.5 cu ft
Bags (60 lb) = 4.5 / 0.5 = 9 bags
Bags (80 lb) = 4.5 / 0.6 = 8 bags
Sand (site-mixed) = 4.5 x 3 = 13.5 cu ft
Reference Table: Mortar Types
| Type | Strength (PSI) | Mix Ratio | Common Use |
|---|---|---|---|
| Type M | 2,500 | 1:0.25:3.75 | Below grade, foundations, retaining walls |
| Type S | 1,800 | 1:0.5:4.5 | Structural walls, exterior at/below grade |
| Type N | 750 | 1:1:6 | General purpose, above grade exterior |
| Type O | 350 | 1:2:9 | Interior, non-load-bearing walls |
| Type K | 75 | 1:3:10 | Historic restoration, soft brick |
Mix ratio = Portland Cement : Lime : Sand (by volume)
Frequently Asked Questions
Which mortar type should I use?
Type N is the most common for general above-grade masonry (walls, chimneys, planters). Type S is required for structural walls and below-grade applications. Type M is used for foundations and retaining walls. Type O is only for interior non-structural work. When in doubt, use Type S — it's suitable for most applications.
How long does mortar take to cure?
Mortar reaches initial set in 2-4 hours and is firm enough for light work in 24 hours. Full strength develops over 28 days. Protect fresh mortar from rain for 24 hours and from freezing for 48 hours. In hot weather, mist the wall lightly to prevent too-rapid drying which weakens the mortar.
What is the correct mortar consistency?
Properly mixed mortar should hold its shape when sliced with a trowel and stick to a vertical surface without sliding. It should be workable but not runny. A common test: draw a line through the mortar with your trowel — the sides should hold their shape without slumping back together.
Can I use mortar mix for concrete projects?
No. Mortar mix lacks the coarse aggregate (gravel) that gives concrete its compressive strength. Mortar is designed to be workable and bond to masonry units, not to bear heavy loads. Use concrete mix for footings, slabs, and structural elements. Use mortar only for laying brick, block, and stone.
How much mortar does a mason use per day?
An experienced mason lays 400-500 standard bricks per day or 100-150 CMU blocks per day. This requires approximately 7-9 bags (80 lb) of mortar for bricks or 10-12 bags for blocks per day. Plan material deliveries accordingly and keep mortar mixed ahead of the mason's pace.
Should I wet bricks before laying them?
It depends on the brick type. Highly absorbent bricks (traditional clay bricks) should be dampened to prevent them from pulling moisture out of the mortar too quickly, which weakens the bond. Modern engineered bricks with low absorption rates should be laid dry. Never soak bricks — surface moisture prevents mortar adhesion.