Mortar Calculator
This mortar calculator finds how much mortar a job needs from the wall area, the joint or bed thickness, and a waste allowance. Enter them and the mortar calculator returns the mortar volume in cubic meters and an approximate bag count. It works as a brick and mortar calculator and a block work estimator, so you can order the right amount for laying or bedding. It works as a masonry mortar calculator and mortar estimator for brick walls, block walls, and bedding.
Results
The Mortar Calculator is part of our Materials Estimating collection. Browse more materials estimating to size, convert, and check your work alongside this tool.
What the mortar calculator shows
Laying brick or block uses mortar in the joints, and the mortar calculator estimates how much. It multiplies the wall area by the joint thickness for a volume, lifts it by a waste allowance for spillage and joint filling, and converts to bags. Whether you run it as a brick and mortar calculator or a blockwork mortar calculator, the method is the same, so it suits walls, paving beds, and repointing.
How the mortar calculator finds volume and bags
The mortar calculator turns area and thickness into a volume, adds waste, then splits it into bags:
The thickness is divided by 1000 to change millimeters into meters. A 25 kg bag of dry mix yields roughly 0.03 cubic meters of mortar, so the mortar calculator divides the volume by that to give the bag count. Site mixed mortar uses the same volume, split by the mortar mix ratio into cement and sand.
Mortar calculator example
A 20 m² wall with 10 mm joints and a 10 percent waste allowance. The mortar calculator gives:
So the wall needs about 0.22 cubic meters of mortar, roughly 8 bags of dry mix. Change the thickness and the mortar calculator updates the amount at once.
How to use the mortar calculator
Enter the wall area in square meters, the joint or bed thickness in millimeters, and a waste allowance as a percent, then the mortar calculator returns the mortar volume and the bag count. Use about 10 mm for brick joints and more for a thick bed. A 10 percent waste allowance suits most jobs, since some mortar is always lost off the trowel.
Reading the mortar calculator result
The volume in cubic meters is what you order site mortar by; the bag count is for ready mix dry bags. Both already include the waste allowance, so buy the whole number of bags shown. Joint thickness has a big effect, since a thick bed uses far more mortar than a thin joint over the same area. For a large job keep a spare bag, and remember the mortar calculator estimates the mortar only, not the bricks or blocks themselves.
When to use the mortar mix calculator
- Laying brick with the mortar mix calculator
- Bedding block with a blockwork mortar calculator
- Sizing a paving bed with a bedding mortar calculator
- Repointing an old wall by area and joint depth
Common mortar calculator mistakes
- Ignoring joint thickness. A thick bed uses far more mortar, so enter the real joint or bed depth.
- Skipping waste. Add about 10 percent, since mortar is always lost off the trowel and in the mixer.
- Counting the bricks here. This estimates mortar only; count the units with a brick tool.
Tips for mortar orders
- Use about 10 mm for brick joints and thicker for block beds.
- Add 10 percent waste and buy a spare bag on big jobs.
- Split the volume by the mix ratio for a site batch.
Brick and mortar calculator and block work
A brick and mortar calculator has to account for how the joints add up. Each brick sits in a bed of mortar and has a perpend joint on its end, so the mortar volume depends on the joint thickness and the size of the units: small bricks mean more joints per square meter and more mortar, while large blocks mean fewer joints and less. That is why a block and mortar calculator usually returns less mortar per square meter than a brick job at the same joint thickness. Estimating by wall area and an average joint thickness, as this tool does, captures both cases well enough for ordering, and adding the waste allowance covers the mortar lost to the trowel and the mixer.
Mortar mix calculator ratios
Site mixed mortar is defined by its ratio of cement to sand, and a mortar mix calculator turns your volume into those parts. A 1 to 4 mix is strong and suits structural brickwork and exposed walls, while a 1 to 5 or 1 to 6 mix is softer and better for internal or historic work, where a rigid mortar can crack the units. Named types follow the same idea: a type s mortar calculator targets a stronger blend for load bearing and below grade work. To use the ratio, take the mortar volume, add roughly a quarter for the sand voids that cement fills, then divide by the sum of the parts for the cement and multiply for the sand. Whether you buy dry bags or batch on site, start from the volume this mortar calculator gives.
Brick and mortar calculator reference
Approximate mortar volume per square meter at common joint thicknesses, for the brick and mortar calculator:
| Joint / bed thickness | Mortar per m² | Bags per 20 m² |
|---|---|---|
| 10 mm | 0.010 m³ | 8 |
| 12 mm | 0.012 m³ | 9 |
| 15 mm | 0.015 m³ | 11 |
| 20 mm | 0.020 m³ | 15 |
Mortar Calculator FAQ
How does the mortar calculator work?
It multiplies the wall area by the joint thickness for a volume, adds a waste allowance, and divides by the yield per bag. The mortar calculator returns cubic meters and bags.
How many bags of mortar do I need?
It depends on area and joint thickness. A 20 m² wall at 10 mm joints needs about 8 bags of dry mix, which the mortar calculator works out with waste included.
What is the mortar mix ratio?
A common mix is 1 part cement to 4 or 5 parts sand for general brickwork. A mortar mix calculator splits the volume by that ratio into cement and sand.
Does it include the bricks?
No. This estimates the mortar only. Use a brick and mortar calculator alongside a brick count to order both the units and the mortar.