How to use the mortar calculator
- Enter the wall. Type the length and the height of the wall. If the wall has doors or windows, enter their total area as openings.
- Choose brick or block. Pick modular brick or 8 × 8 × 16 concrete block. Change the extra allowance if you need to.
- Read the bags. The result shows the 80 lb bags of mortar mix to buy, the same amount in 60 lb and 40 lb bags, and the number of bricks or blocks it covers.
What is a mortar calculator?
A mortar calculator is a tool that estimates how much mortar it takes to lay a wall of brick or block. Mortar is the mix of cement, lime and sand that fills the joints between the units. This calculator counts the units in the wall and divides by the number of units one bag of mortar mix lays.
The answer is in 80 lb bags of pre-mixed mortar, the kind that only needs water.
Features
- Bags of mortar mix for a wall of modular brick or 8 × 8 × 16 concrete block
- Door and window openings taken out of the wall
- The same amount of mix in 80 lb, 60 lb and 40 lb bags
- The number of bricks or blocks the mortar covers
- For brick, the volume of mortar in cubic feet
- An extra allowance that starts at 15% and can be changed
- A cost from your own price per bag, a PDF of the estimate and a WhatsApp share button
What you can use it for
- A brick wall in modular brick
- A wall of 8 × 8 × 16 concrete block
- Checking how many bags to buy before a weekend job
- Comparing 80, 60 and 40 lb bags
How the mortar is calculated
Units = (wall length × wall height − openings) × units per square foot × (1 + allowance ÷ 100), rounded up.
Bags of 80 lb = units ÷ units per bag, rounded up.
| Unit | Units per square foot | Units per 80 lb bag | Square feet per 80 lb bag |
|---|---|---|---|
| Modular brick | 6.75 | up to 37 | about 5.5 |
| Concrete block, 8 × 8 × 16 | 1.125 | up to 13 | about 11.6 |
The units per bag are from Quikrete's data sheet for Mortar Mix (product 1102, revised November 2020): each 80 lb bag lays up to 37 standard bricks or 13 standard 8 inch by 8 inch by 16 inch blocks. The last column is the units per bag divided by the units per square foot.
Worked example: a 20 ft by 8 ft brick wall
- Wall area: 20 × 8 = 160 square feet.
- Modular bricks: 160 × 6.75 = 1,080.
- With a 15% allowance: 1,080 × 1.15 = 1,242 bricks.
- 80 lb bags: 1,242 ÷ 37 = 33.6, so 34 bags.
- The same mix in 60 lb bags: 45 bags. In 40 lb bags: 68 bags.
The same wall in 8 × 8 × 16 block is 180 blocks, 207 with the allowance, and 207 ÷ 13 = 15.9, so 16 bags.
Why the allowance starts at 15%
Quikrete's figures say "up to", so they are the most a bag will lay. The Brick Industry Association's Technical Note 10 says to add 15 to 25 percent to the net mortar quantity for waste. The calculator starts at the low end, 15%, and you can raise it.
The smaller bag counts are worked out by weight: the pounds of mix in the 80 lb bags, divided by 60 or 40. The data sheet gives a yield only for the 80 lb bag.
What the calculator includes
- Only modular brick and 8 × 8 × 16 block are covered. For mortar mixed on site from masonry cement and sand, see the figures in the concrete block calculator.
- Grout for filling block cores is not included.
- Each dimension can be up to 10,000 in its unit, the openings up to 1,000,000 and the allowance 0 to 50%.
Is it private?
Yes. The calculation and the PDF are made in your browser. The numbers you type are not sent to our server and are not saved.
Tips for an accurate estimate
- Choose the unit you are laying: brick or block need very different amounts of mortar.
- Keep the extra mortar allowance; mortar is lost on the board, in the joints and on the ground.
- Mix only what you can use before it starts to stiffen.
- Use the same water amount in every batch so the joints look the same.
- Check the bag label: some mortar types lay more units per bag than others.
Related calculators
Frequently asked questions
- How much mortar do I need?
- Count the bricks or blocks and divide by the number one bag lays. Quikrete's Mortar Mix data sheet says an 80 lb bag lays up to 37 standard bricks or 13 standard blocks. A 20 ft by 8 ft modular brick wall with a 15% allowance needs 34 bags.
- How many bricks does a bag of mortar lay?
- Up to 37 standard bricks per 80 lb bag, according to the Quikrete Mortar Mix data sheet (product 1102).
- How many blocks does a bag of mortar lay?
- Up to 13 standard 8 inch by 8 inch by 16 inch blocks per 80 lb bag, according to the same Quikrete data sheet.
- How many bags of mortar do I need for 100 blocks?
- 100 ÷ 13 = 7.7, so 8 bags of 80 lb mortar mix at the data sheet's best yield. With a 15% allowance it is 115 ÷ 13 = 8.8, so 9 bags.
- How many bags of mortar do I need for 1,000 bricks?
- 1,000 ÷ 37 = 27.03, so 28 bags of 80 lb mortar mix at the data sheet's best yield. With a 15% allowance it is 1,150 ÷ 37 = 31.1, so 32 bags.
- How much mortar waste should I allow?
- The Brick Industry Association says to add 15 to 25 percent to the net mortar quantity. The calculator starts at 15%.
Sources
Every figure this calculator uses comes from the published sources below. The formulas are on this page, so any result can be checked by hand.
- Quikrete, Mortar Mix No. 1102: data sheet (revised November 2020). One 80 lb bag lays up to 37 standard bricks or 13 standard 8 × 8 × 16 in blocks.
- Brick Industry Association, Technical Note 10. Bricks per square foot by brick size, mortar per 1,000 bricks, 5% brick waste and 15 to 25% extra mortar.