How to estimate mortar
- Count the units. Standard 8 × 8 × 16 in concrete block takes 1.125 blocks per sq ft of wall; modular brick takes about 6.75 per sq ft. If you already have a count from the brick calculator, enter it directly.
- Divide by the bag yield. Premixed mortar bags state how many units they lay.
- Or use the masonry cement rule if you mix masonry cement with sand on site.
- Add about 10% for droppings, cleanup and joint variation.
Premixed mortar yield
Bagged mortar mixes already contain sand; you add only water. Manufacturer data for a typical 80 lb bag of Type S or N mortar mix is up to about 13 standard 8 × 8 × 16 in blocks or 37 standard bricks per bag.
| Unit | Units per sq ft | Approx. units per 80 lb bag | 80 lb bags per 100 sq ft |
|---|---|---|---|
| 8 × 8 × 16 in block | 1.125 | 13 | 9 |
| 12 × 8 × 16 in block | 1.125 | 13 | 9 |
| 4 × 8 × 16 in block | 1.125 | 13 | 9 |
| Modular brick | 6.75 | 37 | 19 |
| Queen / oversized brick | 5.8 | 32 | 19 |
| Utility brick | 3.0 | 26 | 12 |
Block is normally laid with mortar on the face shells only, so the yield is about the same for 4, 8 and 12 in wide block. Figures for queen and utility brick are scaled from the masonry-cement rule for those sizes; check your product's label.
Worked example: a 100 sq ft block wall
A 100 sq ft wall of 8 × 8 × 16 in block needs 113 blocks. At 13 blocks per bag, that is 8.7 bags; with 10% extra, buy 10 bags of 80 lb premixed mortar.
Mixing your own: masonry cement and sand
On larger jobs masons usually mix masonry cement (or portland cement and lime) with sand. Common rules of thumb are about 3 bags of masonry cement per 100 blocks and about 7 bags per 1,000 modular bricks (more for larger brick), with roughly 1 cubic yard of sand for every 7 bags. In volume terms, a 100 sq ft block wall uses around 8.5 cu ft of mortar.
Mortar types N, S and M
| Type | Typical use |
|---|---|
| N | General above-grade walls, veneer and interior masonry; workable and flexible |
| S | Below-grade and foundation walls, retaining walls, and where higher bond and strength are needed |
| M | Heavy loads and below-grade work in contact with soil; strongest, least workable |
Use the type your plans or local code specify. Mortar should generally be weaker than the units it binds so cracks form in replaceable joints rather than in the brick or block.
Tips
- Mix only what you can use in about 1½–2 hours; don't retemper mortar that has started to set.
- Keep joints a consistent ⅜ in — thicker joints use mortar quickly and change the course height.
- Cores that will be grouted with rebar need grout or concrete, not mortar; estimate it with the concrete calculator.
Frequently asked questions
How many bags of mortar do I need for 100 blocks?
About 8 bags of 80 lb premixed mortar at 13 blocks per bag, or about 3 bags of masonry cement mixed with sand.
How many bricks does a bag of mortar lay?
An 80 lb bag of premixed mortar lays up to about 37 standard bricks, depending on joint size and waste.
How much mortar for 1,000 bricks?
About 27 bags of 80 lb premixed mortar before waste, or about 7 bags of masonry cement plus 1 cubic yard of sand.
How much sand do I need for mortar?
About 1 cubic yard of mason sand for every 7 bags of masonry cement.
Type N or Type S mortar?
Type N for most above-grade walls and veneer; Type S for foundations, below-grade and retaining walls or where specified for strength.
Sources & standards
This calculator's formulas and default values are based on the following codes, standards and published data. Codes are adopted and amended locally, so check with your building department for permitted work. See how we build and check our calculators.
- QUIKRETE Mason Mix data sheet: 80 lb bag lays up to 37 standard bricks or 13 standard 8 × 8 × 16 in blocks.
- Masonry supplier estimating guides (for example, Titan America Block Estimating Guide): 3 bags per 100 block, 7 bags per 1,000 modular brick, 1 cu yd sand per 7 bags.
- ASTM C270, Standard Specification for Mortar for Unit Masonry: mortar types M, S, N and O.