How many bags of mortar do I need?
Type the wall length and height and pick bricks or 8 in blocks. The mortar calculator counts the units, works out the mortar in the joints, and turns the count into 80 lb bags of mortar mix from the maker’s stated yield.
- 80 lb bags of mortar mix
- 18
For 549 bricks, buy about 18 80 lb bags of mortar mix.
- Bricks or blocks
- 549
- Mortar volume (ft³)
- 4.8695
- Mortar volume (yd³)
- 0.180352
- Mortar per unit (in³)
- 13.9336
- Wall area (ft²)
- 80
- Units
- bricks
80 lb bags of mortar mix: 18. For 549 bricks, buy about 18 80 lb bags of mortar mix.
How to calculate
Estimates the bricks or blocks in a wall, the mortar volume for their joints, and the 80 lb bags of mortar mix to buy, from the wall size, unit size, joint thickness and waste.
Example with the default inputs (Wall length (ft) 20, Wall height (ft) 4, Laying Bricks, Joint thickness (in) 0.375, Waste allowance 10%): For 549 bricks, buy about 18 80 lb bags of mortar mix.
Method: Units = ⌈144 × wall area (ft²) ÷ ((l + j)(h + j))⌉; mortar = units × ((l + j)(h + j) − l h) × d × (1 + waste) ÷ 1,728 ft³; bags = ⌈units × (1 + waste) ÷ units per bag⌉.
- A single-wythe wall, each unit with one bed joint and one head joint; cores of hollow blocks are not filled.
- Standard sizes: modular brick 7 5/8 × 2 1/4 × 3 5/8 in, concrete block 15 5/8 × 7 5/8 × 7 5/8 in, with 3/8 in joints.
- Bags use the maker’s yield (Sakrete Type S and Type N: 35 bricks or 12 blocks per 80 lb bag); yields vary with the joint and the mason.
- The waste allowance is yours to set; the default 10% is not from a maker.
Worked examples
Each example is checked against the calculator on every build.
- Wall length (ft) 20, Wall height (ft) 4, Laying Bricks, Joint thickness (in) 0.375, Waste allowance 10% gives Bricks or blocks 549, 80 lb bags of mortar mix 18, Mortar per unit (in³) 13.933594, Mortar volume (ft³) 4.869501, Wall area (ft²) 80.Source: Sakrete, Mortar Mix Type S (an 80 lb bag lays 12 standard 8 in blocks or 35 standard bricks), https://www.sakrete.com/product/mortar-mix-type-s/ (retrieved 2026-10-02)
- Wall length (ft) 32, Wall height (ft) 6, Laying 8 in blocks, Joint thickness (in) 0.375, Waste allowance 0% gives Bricks or blocks 216, 80 lb bags of mortar mix 18, Mortar per unit (in³) 67.552734, Mortar volume (ft³) 8.444092, Mortar volume (yd³) 0.312744.Source: Sakrete, Mortar Mix Type N (an 80 lb bag lays 12 standard 8 in blocks or 35 standard bricks), https://www.sakrete.com/product/mortar-mix-type-n/ (retrieved 2026-10-02)
- Wall length (ft) 10, Wall height (ft) 3, Laying Bricks, Joint thickness (in) 0.5, Units per 80 lb bag (optional) 37, Waste allowance 5% gives Bricks or blocks 194, 80 lb bags of mortar mix 6, Mortar per unit (in³) 18.804688.Source: Sakrete, Mortar Mix Type S (an 80 lb bag lays 12 standard 8 in blocks or 35 standard bricks), https://www.sakrete.com/product/mortar-mix-type-s/ (retrieved 2026-10-02)
How it works
Wall length and height are in feet; unit sizes and the joint j are in inches. A unit has length l, height h and depth d (the wall thickness).
- Wall area = length × height (ft²), or 144 × that in in²
- Units = ⌈144 × area ÷ ((l + j)(h + j))⌉: each unit with its joint covers (l + j)(h + j)
- Mortar per unit = ((l + j)(h + j) − l × h) × d in³: one bed joint and one head joint, the full depth of the unit
- Mortar volume = units × mortar per unit × (1 + waste ÷ 100) ÷ 1,728 ft³, and ÷ 27 more for yd³
- Bags = ⌈units × (1 + waste ÷ 100) ÷ units per bag⌉
Every step uses exact fractions of the typed decimals, so a wall that takes exactly a whole number of units is not rounded up by one.
Assumptions
- Sizes (unless you type your own): modular brick 7 5/8 × 2 1/4 × 3 5/8 in; concrete block 15 5/8 × 7 5/8 × 7 5/8 in (an 8 × 8 × 16 in nominal block); joint 3/8 in.
- Coverage: 35 bricks or 12 blocks per 80 lb bag, from Sakrete’s Type S and Type N mortar mix pages. Type another maker’s yield to use it.
- Waste: 10% by default; this allowance is not from a maker.
- A single wythe (one unit thick). Openings are not taken out, and hollow block cores are not filled.
Rules
- Wall length is from 0.01 to 100,000 ft and height from 0.01 to 1,000 ft; unit sizes from 0.01 to 100 in; the joint from 0.01 to 2 in; units per bag from 0.1 to 10,000; waste from 0% to 100%.
Output format. Bags and units as whole numbers; volumes and mortar per unit to 6 significant digits; the area to 10.
Worked examples by hand
20 × 4 ft of brick, 3/8 in joints, 10% waste. Area 80 ft² = 11,520 in². Face per brick (7.625 + 0.375)(2.25 + 0.375) = 8 × 2.625 = 21 in², so 11,520 ÷ 21 = 548.6 → 549 bricks. Mortar per brick (21 − 17.15625) × 3.625 = 13.9336 in³; 549 × 13.9336 × 1.1 ÷ 1,728 = 4.8695 ft³. Bags: 549 × 1.1 ÷ 35 = 17.25 → 18.
32 × 6 ft of 8 in block, no waste. 192 ft² = 27,648 in²; face (15.625 + 0.375)(7.625 + 0.375) = 16 × 8 = 128 in², so 216 blocks exactly. Mortar per block (128 − 119.140625) × 7.625 = 67.5527 in³; total 8.44409 ft³ (0.312744 yd³). Bags: 216 ÷ 12 = 18.
10 × 3 ft of brick, 1/2 in joints, 37 bricks per bag, 5% waste. 4,320 in² ÷ (8.125 × 2.75) = 193.3 → 194 bricks; mortar per brick (22.34375 − 17.15625) × 3.625 = 18.8047 in³. Bags: 194 × 1.05 ÷ 37 = 5.51 → 6.
Other questions people ask
How many bags of mortar do I need for bricks?
Sakrete says an 80 lb bag of its Type S or Type N mortar mix lays 35 standard bricks. Divide your brick count by 35 and round up, after adding a waste allowance. A 20 × 4 ft wall takes 549 bricks, so 549 × 1.1 ÷ 35 = 17.3, or 18 bags.
How many blocks does an 80 lb bag of mortar lay?
Sakrete gives 12 standard 8 in blocks per 80 lb bag for its Type S and Type N mortar mixes. A 32 × 6 ft block wall has 216 blocks, so 18 bags before any waste.
How do I calculate the number of bricks in a wall?
Divide the wall area by the face of one brick plus one joint. A modular brick is 7 5/8 × 2 1/4 in; with 3/8 in joints that is 8 × 2 5/8 = 21 in², so a square foot (144 in²) holds 144 ÷ 21 = 6.86 bricks.
How is the mortar volume worked out?
Each unit gets one bed joint and one head joint. The mortar per unit is ((length + joint) × (height + joint) − length × height) × depth. For a modular brick with 3/8 in joints: (21 − 17.156) × 3.625 = 13.93 in³.
How much waste should I allow?
The page uses 10% unless you change it; the makers’ pages give no waste figure. Mortar is lost to droppings, spills and batches that set before use, so beginners often allow more.
Should I use Type S or Type N mortar?
Sakrete titles its Type S mix for laying wall blocks and its Type N mix for brick laying and joint repair. Follow your plans or local code; on Sakrete’s pages both lay the same number of units per bag.