How to use the mortar calculator
- Choose standard 8 × 8 × 16 in concrete blocks or standard bricks.
- Enter how many you will lay. If you do not know yet, get the count from the concrete block calculator or the brick calculator.
- Keep about 10% extra for droppings, mortar that stiffens before use, and the first batches while you get the mix right.
Mortar cannot be used once it starts to set, so Decoratoradvice suggests mixing only what you can lay in the next hour or two.
Mortar formula
Bags = units ÷ units per bag × (1 + extra), rounded up
The units-per-bag figures come from the QUIKRETE Mason Mix data sheet: an 80 lb bag "will lay up to 37 standard bricks or 13 standard (8 in by 8 in by 16 in) blocks". "Up to" means the best case, so the waste allowance matters.
Worked examples
100 concrete blocks:
100 ÷ 13 = 7.69 bags
With 10% extra: 8.46, so 9 bags
500 bricks:
500 ÷ 37 = 13.5 bags
With 10% extra: 14.9, so 15 bags
Mortar is not grout
Mortar bonds bricks and blocks together. Tile grout fills the joints between tiles and is a different product; the grout calculator covers tile joints. Concrete for footings and slabs is a third product; see the concrete calculator.
Tips
- Mix only what you can use before it stiffens. Mortar that has started to set should not be remixed with extra water; follow the bag instructions.
- Keep the bag count rounded up. Running short mid-wall leaves a visible change in joint colour when you restart with a new batch.
- Wider or tooled joints use more mortar than the manufacturer's best case.
Common mistakes
- Using the best-case yield with no extra. Actual coverage is usually lower.
- Counting blocks per square foot instead of total blocks. This calculator needs the total number of units.
- Using concrete mix as mortar. Concrete contains gravel and is not made for masonry joints.
Frequently asked questions
How many blocks does an 80 lb bag of mortar lay?
Up to 13 standard 8 × 8 × 16 in blocks, according to QUIKRETE's Mason Mix data sheet.
How many bricks does an 80 lb bag of mortar lay?
Up to 37 standard bricks, per the same data sheet.
How much mortar do I need for 1,000 bricks?
1,000 ÷ 37 = 27.03, so 28 bags before waste, or 30 bags with 10% extra. As a volume check, the Brick Industry Association lists about 8.1 cu ft of mortar per 1,000 modular bricks.
Why add 10% extra?
Mortar is lost to droppings, cleaning joints and batches that stiffen. The bag yield is also a best case.
Can I use the same mortar for brick and block?
Many bagged masonry mixes are sold for both. Follow the product label and any mortar type your plans specify.
Key takeaways
- An 80 lb bag of QUIKRETE Mason Mix lays up to 13 blocks or 37 bricks.
- Divide your unit count by that figure and add about 10%.
- Round up so you do not run short mid-wall.
- Mortar, grout and concrete are different products.
Sources
- QUIKRETE Mason Mix (No. 1136) data sheet
- Brick Industry Association, Technical Note 10: mortar per 1,000 bricks.