How Many Bags of Mortar Per 100 Blocks? Yield Guide

You need about 3 bags of masonry cement mixed with sand, or roughly 8 to 10 bags of pre-mixed 80 lb mortar, to lay 100 standard 8 by 8 by 16 inch concrete blocks with 3/8 inch joints and face-shell bedding. The count depends entirely on which product you buy, so below is the math for both, the bag counts by size, costs, and a calculator that does it for you.

The short answer: bags of mortar per 100 block

The count splits into two products that people both call mortar. Masonry cement is a bag of cement you mix with your own sand, and the trade rule is 3 bags per 100 block. Pre-mixed mortar already has the sand blended in, so each bag does less and you need more of them.

For pre-mixed, plan on about 8 to 10 bags of 80 lb or 12 to 14 bags of 60 lb per 100 standard blocks. These figures assume a standard 3/8 inch joint and face-shell bedding, where mortar sits only on the outer edges of the block.

Product per 100 block	Bags needed	Notes
Masonry cement + sand	3 bags	Add about 0.4 cu yd sand
Pre-mixed 80 lb	8 to 10	3/8 in joint, face-shell
Pre-mixed 60 lb	12 to 14	3/8 in joint, face-shell

To skip the conversions, drop your block count and joint size into the mortar calculator and it returns bags by size and the sand needed for the cement method.

Mortar volume per block and the 3/8 inch joint

Everything starts from one number: how much mortar a single block uses. For a standard 8 by 8 by 16 inch CMU with face-shell bedding and a 3/8 inch joint, plan on about 0.057 cubic feet of mortar per block, a figure consistent with National Concrete Masonry Association practice.

So 100 blocks need about 5.7 cubic feet net. Add 10% for waste, droppings and tooling losses and you land near 6.3 cubic feet of mortar for the wall.

Mortar (ft3) = Blocks x 0.057 x 1.10 (waste)

The joint size drives this. The masonry standard is a 3/8 inch joint, and going thicker quietly burns through extra bags. If you are estimating block counts first, the concrete block calculator gives the wall area in blocks before you size the mortar.

Pre-mixed mortar: how many 80 lb and 60 lb bags

Pre-mixed bags are the simplest route for a small to mid wall, since you just add water. The catch is yield: an 80 lb bag of pre-mixed mortar makes roughly 0.67 cubic feet, and a 60 lb bag about 0.45 cubic feet.

Divide the 6.3 cubic feet for 100 blocks by those yields and you get about 10 bags of 80 lb or 14 bags of 60 lb. Manufacturer rules of thumb run a touch leaner, often quoting 10 to 12 blocks per 80 lb bag, which is where the 8 to 10 bag figure comes from.

Bag size	Yield per bag	Blocks per bag	Bags per 100 block
80 lb	0.67 ft3	10 to 12	8 to 10
60 lb	0.45 ft3	7 to 8	12 to 14
40 lb	0.30 ft3	5	20

Yield varies by brand and how heavy your hand is on the trowel. Always check the coverage printed on your specific bag and buy 5 to 10% extra, because you cannot run short halfway up a course.

Stacked pallets of concrete blocks beside bags of mortar mix at a residential masonry job site

Masonry cement method: 3 bags plus sand

Compare options only after defining the specified mortar type, product yield and measured block quantity.

That works out to roughly 0.4 cubic yards of mortar sand per 100 blocks. A common mix is 1 bag of 70 lb Type N masonry cement to about 18 to 20 shovels of masonry sand and 4 to 5 gallons of clean water.

Type N suits most above-grade walls; Type S is the higher-strength choice for foundations, retaining walls and anything below grade. If you are also filling cores or a bond beam, the concrete calculator handles the grout and fill volume separately from the mortar in the joints.

Face-shell vs full bedding and what it costs

Bedding type changes the count more than people expect. Face-shell bedding, mortar on the outer shells only, is standard for most load-bearing CMU walls and is what the 8 to 10 bag figure assumes. Full bedding, where you butter the entire block face, uses roughly 60% more mortar.

So 100 blocks with full bedding can climb to about 22 bags of 60 lb, used on the first course, on solid units, or where codes call for it. Confirm what your design requires before you buy.

By Calcnaut

Formula and declared-case checks run during the build; sources are listed for readers to review. Read our method and editorial policy.

Published 2026-06-29 Updated 2026-09-13

Frequently asked questions

How many bags of mortar do I need for 100 concrete blocks?

You need about 3 bags of masonry cement mixed with sand, or roughly 8 to 10 bags of pre-mixed 80 lb mortar, to lay 100 standard 8 by 8 by 16 inch blocks at 3/8 inch joints with face-shell bedding.

How many blocks will one 80 lb bag of mortar lay?

One 80 lb bag of pre-mixed mortar lays about 10 to 12 standard concrete blocks at a 3/8 inch joint with face-shell bedding. Yield drops with thicker joints or full bedding, so check the figure printed on your bag.

What is the rule of thumb for mortar per 100 block?

The trade rule of thumb is 3 bags of masonry cement per 100 block, plus about one cubic yard of sand for every 7 bags of cement. This assumes you mix the mortar yourself rather than buying pre-mixed bags.

How much sand do I need to mix mortar for 100 blocks?

You need about 0.4 cubic yards of masonry sand for 100 blocks, based on one cubic yard of sand per 7 bags of mortar cement. Mix roughly 18 to 20 shovels of sand per 70 lb bag of masonry cement.

Should I use Type N or Type S mortar for block?

Use Type N mortar for most above-grade block walls and Type S for foundations, retaining walls and below-grade work that needs higher compressive strength. Both meet ASTM C270 and come in pre-mixed bags.

Sources and references

These references and structured source records support the method and material data used on this page.

How Many Bags of Mortar Per 100 Block?

Key takeaways