Block Mortar Calculator Mortar Bags for CMU Joints

Estimate whole 60-lb or 80-lb pre-mix mortar bags from wall dimensions or a known block count.

The 80-lb default starts from a manufacturer-published coverage of about 13 standard blocks; edit either bag coverage to match the product you will buy.

Estimate Block Mortar

Use this for the joint mortar between blocks. To count the blocks themselves, use the standard concrete block calculator instead. Filling cores? Use the block fill calculator.

Unit:

Wall Input

Start from:

Wall Length (ft)

Wall Height (ft)

Primary bag size:

Current mortar order

16 x 80-lb

180 base blocks / 13 blocks per bag + 10% order buffer

Base block count: 180
Selected coverage: 13 blocks per bag

Bag and Product Coverage

80-lb Coverage (blocks per bag)

60-lb Coverage (blocks per bag)

The 80-lb default of 13 follows the QUIKRETE Mortar Mix 1102 data sheet. The 60-lb value is a separate planning default. Check the yield printed on the actual bag and edit either value when it differs.

Order Buffer

10%

Extra purchasing capacity only. Product coverage already reflects the product's stated laying yield.

Cost Estimation

Enable to enter your local mortar bag price. Price does not change the quantity estimate.

What the mortar estimate covers

The bag estimate covers the horizontal bed joints and vertical head joints used to lay standard hollow CMU. The labels below spell out the boundary without relying on color.

Bed joint: included
Head joint: included
Hollow core
Core fill: excluded

This calculator estimates pre-mix mortar for standard CMU bed and head joints. It excludes grout or concrete core fill, which belongs in the block fill calculator. The diagram explains quantity scope only and does not show structural design or approve a mortar type.

How this block mortar calculator works

Wall mode turns area into a block count with the nominal 8 x 16 inch face module, including the mortar joint. If you already have a takeoff, enter the whole-block count instead.

The calculator adds the order buffer, divides that coverage target by the blocks-per-bag value, then rounds up because mortar is sold by the whole bag. Product yield, pre-mix versus masonry cement, block geometry, head joints, and joint profile can all change the answer. Use the coverage printed for the product you will buy.

The scope does not include brick, pointing or repointing, thinset, AAC, stone, paver work, core fill, site-mix recipes, or structural design. It also does not calculate Portland cement, lime, sand, or total mixed-mortar quantities.

Wall to blocks: base blocks = round up(wall area x face-module rate)
Blocks to bags: coverage target = round up(base blocks x (1 + order buffer %)); bags = round up(coverage target / product coverage)

Worked example for 100 standard blocks

Use the 80-lb default of 13 blocks per bag. The displayed bag totals come from the same calculation used by the tool, so they change with the shared coverage contract.

No order buffer

8 whole 80-lb bags

Round up 100 blocks / 13 blocks per bag

10% order buffer

9 whole 80-lb bags

Round up 110 blocks / 13 blocks per bag

Mortar types and ASTM C270

Types O, N, S, and M are specification classes under ASTM C270. Changing the letter does not change the bag count because quantity comes from the product coverage.

Type	Explanatory boundary
O	A lower-compressive-strength class with limited uses. The project documents must say when it is suitable.
N	A medium-compressive-strength class often specified for general unit masonry. This page does not decide whether it fits the wall.
S	A higher-compressive-strength and higher-bond-strength class. Structural and exposure requirements belong in the project specification.
M	The highest-compressive-strength class in this table. Its name is not a reason to substitute it for the specified mortar.

Use the mortar type and property or proportion specification named in the plans, project specifications, and local code. Do not use this table as structural design advice, and do not alter a packaged product with a site-mix recipe to imitate another type.

Sources

The 80-lb default uses the QUIKRETE Mortar Mix 1102 data sheet for approximately 13 standard 8 x 8 x 16 inch blocks. The 60-lb value is an editable planning default, not a universal product claim. Last reviewed July 2026.

Frequently asked questions

What should I enter if the bag does not list blocks per bag?

Check the product data sheet or ask the manufacturer or supplier for coverage for your block and joint profile. Keep the field editable rather than treating a planning default as a product guarantee.

Can I compare pre-mix bags with masonry cement bags?

Not by bag count alone. Pre-mix includes the dry ingredients for that product, while masonry cement is combined with job-site sand under a specified mix. Compare the manufacturer's yield and the project specification for the system you will use.

What should I do with the extra capacity on a small project?

Check whether the required mortar is sold in a smaller package and confirm the minimum practical order with the supplier. Extra capacity describes unopened product. Do not plan to store mixed mortar for later work.

For the same standard CMU wall, continue with the calculator that owns the next task: