Calculate masonry mortar volume, bags and cost
Estimate bed and head-joint mortar for rectangular bricks or concrete blocks. Enter actual unit dimensions, joint thickness and the packaged yield you will purchase.
Enter wall, unit and product data, then select Calculate.
Use actual masonry-unit dimensions, not nominal module dimensions. Packaged yield varies by bag weight, formulation and mixing water; replace the example value with the product label.
How to use this mortar calculator
- Enter net wall area or calculate gross wall area from length, height and number of walls, then subtract all openings.
- Enter actual brick or block length, height and wall depth. Do not include the mortar joint in those dimensions.
- Enter the planned bed/head-joint thickness and an allowance for waste.
- Replace packaged yield and price with the current values from the bag you will purchase.
- Calculate and compare theoretical volume with whole-bag quantity.
Mortar calculation formula
Module face = (unit length + joint) × (unit height + joint). Joint fraction = 1 − unit face ÷ module face. Mortar volume = net wall area × wall depth × joint fraction. Order volume = mortar volume × (1 + allowance ÷ 100). Bags = order volume ÷ packaged yield, rounded up.
The module method counts the crossing of horizontal and vertical joints once. It treats each masonry unit as its outer rectangular prism; hollow cores are not assumed to be filled.
Worked example
A 100 ft² single-wythe wall using actual 7.625 × 2.25 × 3.625 in bricks and 3/8 in joints has an estimated joint share of 18.304%. The theoretical mortar volume is about 5.529 ft³. With 10% extra, order about 6.082 ft³. At 0.7 ft³ per bag, purchase 9 bags.
Six calculated examples
| Net wall area | Mortar with allowance | Bags |
|---|---|---|
| 50 ft² | 3.041 ft³ | 5 |
| 100 ft² | 6.082 ft³ | 9 |
| 150 ft² | 9.123 ft³ | 14 |
| 200 ft² | 12.164 ft³ | 18 |
| 300 ft² | 18.246 ft³ | 27 |
| 500 ft² | 30.411 ft³ | 44 |
Assumptions and limits
This is a quantity estimate for uniform rectangular brick or block walls. It does not account separately for bond pattern, partial units, wall ties, reinforcement, lintels, cavities, grout-filled cells, tooling loss, site mixing, pointing or irregular stone. Actual bag yield changes with water content, consolidation and waste. Confirm mortar type, joint geometry and yield with the project specification and supplier.
The tool estimates material quantity only; it does not design masonry or verify structural capacity, fire resistance or code compliance.
Frequently asked questions
Can I use this for concrete blocks?
Yes. Enter the block’s actual outside length, height and wall depth plus the planned joint thickness. Do not enter nominal modular dimensions as the unit dimensions.
Does it include grout inside block cells?
No. The calculation covers bed and head joints only. Filled cells require a separate structural grout calculation based on the block geometry and reinforcement plan.
Why should I enter bag yield?
Bag weights and mortar formulations differ. The manufacturer’s stated mixed yield is more reliable than assuming that every bag produces the same volume.