Concrete & Masonry
Mortar Calculator
Estimate how much mortar you need for brick or block work. Enter the number of bricks or blocks, or the wall area, and this mortar calculator works out the mortar volume from the joint size, adds a waste allowance, and tells you how many bags of mortar mix to buy.
Result
Enter your measurements and press Calculate. What to buy, the working and the cost will appear here.
How to use the mortar calculator
- Choose the brick or block you are laying.
- Enter how many bricks or blocks, or the wall area if you have not counted them yet.
- Check the joint: 3/8 in (10 mm) is standard.
- Pick the mortar bag, enter the yield from the bag if it differs, and set the waste allowance.
- Press Calculate for mortar volume, bags and cost.
How mortar is calculated
Mortar fills the joints around each unit, so the amount depends on the unit size, the joint thickness and how the unit is bedded:
- Brick and solid block are fully bedded. Mortar per unit = (unit face plus joint − unit face) × unit depth.
- Hollow block is usually bedded on its two face shells only, so it takes far less mortar per block.
bags = units × mortar per unit × (1 + waste) ÷ yield per bag
A modular brick with 3/8 in joints takes about 13.9 in³ of mortar, so 1,000 bricks need about 8 ft³ before waste.
Worked example: mortar for 1,500 bricks
A brick planter and garden wall uses 1,500 modular bricks with 3/8 in joints. Mortar comes in 80 lb bags at $9.50, and we allow 25% for droppings and cleanup:
- Per unit: ((8 in × 2.625 in) − (7.625 in × 2.25 in)) × 3.625 in deep = 13.9 in³
- Total: 1,500 × 13.9 in³ × 1.25 = 15.12 ft³
- Bags: 15.12 ft³ ÷ 0.67 ft³ per bag → 23 bags
Mortar bags: 23 bags; Mortar volume: 15.12 ft³; Weight to carry: 1,840 lb; Estimated cost: $218.50. Open this example in the calculator.
Mortar rules of thumb
| Work | Typical mortar |
|---|---|
| 1,000 modular bricks, 3/8 in joints | about 8 ft³, or 16 bags of 80 lb mix with 25% waste |
| 100 standard 8 in hollow blocks | about 1.3 ft³, or 2–3 bags of 80 lb mix with waste |
| 1 m² of UK brickwork (60 bricks) | about 0.018 m³ (18 L) before waste |
Mortar types
- Type N: general-purpose mortar for above-grade walls, veneer and interior work.
- Type S: stronger, for below-grade work, foundations, retaining walls and patios.
- Type M: the strongest, for heavy loads and below-grade structural work.
Your plans or local code say which type to use. Premixed mortar mix only needs water; masonry cement is mixed with sand on site, which changes the yield per bag.
How much waste to allow
Mortar is the most wasted material on a masonry job: some is dropped, some stiffens before use, and some is scraped off when joints are tooled. Professionals often allow 10–15%; DIY bricklayers should allow 25% or more.
Assumptions and limitations
- Joints are full and even. Collar joints between two wythes and grout in block cores are not included.
- The bag yield is a typical figure for premixed mortar; enter your bag’s yield for an exact count.
- The wall-area option counts units from the same joint size, so enter net area after openings.
Mortar questions
How many bags of mortar do I need for 1,000 bricks?
About 12 bags of 80 lb premixed mortar for the joints alone, or 16 with a 25% waste allowance.
How many blocks does a bag of mortar lay?
About 40 standard hollow blocks per 80 lb bag with a normal waste allowance; more if little is dropped.
How much mortar does an 80 lb bag make?
Typically about 0.6–0.7 cubic feet of mixed mortar. Check the bag, as products differ.
Formulas, unit conversions and default values are explained on our methodology page. Results are estimates; check manufacturer data and local codes before you buy or build.