Block Mortar Calculator

A block mortar calculator returns the number of 80 lb mortar mix bags for a known count of concrete blocks or standard bricks. It divides the unit count, after a 10% waste allowance by default, by the QUIKRETE yield of 13 blocks or 37 bricks per bag, then rounds up to a whole bag.

Last reviewed September 2026Method & sources Report an error

Units per Bag (manufacturer yield)

Includes a 10% waste allowance.

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Mortar mix43 80 lb bags

Breakdown
Units per Bag (manufacturer yield)	13
Mortar Mix Bags (80 lb)	43
Estimated Cost

How to Calculate Block Mortar

This calculator is a direct application of QUIKRETE's own published Mortar Mix yield. One 80 lb bag lays up to 13 standard 8x8x16 concrete blocks, or up to 37 standard bricks. Given a unit count, the raw bags needed is unit count ÷ yield per bag. A waste allowance is added first to cover mortar lost to spillage, over-buttering, and tooling squeeze-out. The result is then rounded up to a whole bag, since a partial bag isn't purchasable.

Example: 500 standard 8x8x16 blocks, at 10% waste

500 standard 8x8x16 blocks, at 10% waste: 1. Adjusted unit count: 500 × 1.10 = 550 blocks 2. Bags needed: 550 ÷ 13 = 42.3, rounded up to 43 bags (80 lb QUIKRETE Mortar Mix) For comparison, 1,000 standard bricks at the same 10% waste would need 1,100 ÷ 37 = 29.7, rounded up to 30 bags. That is fewer bags despite twice the unit count, since a brick's mortar joint uses far less material than a block's.

Block Mortar: Compare Scenarios

Scenario	Units per Bag (manufacturer yield)	Mortar Mix Bags (80 lb)
Small (100 blocks, patch or small repair)	13	9
Medium (500 blocks, garage wall)	13	43
Large (2,000 blocks, full foundation wall)	13	170

What Is Block Mortar?

A block mortar calculator answers a narrower question than a full wall takeoff. If you already know how many blocks or bricks you're laying, from a supplier quote, a material list, or a repair job, how many bags of mortar mix does that call for? It's built for exactly that situation, rather than requiring wall dimensions the way the Concrete Block calculator's combined takeoff does.

Block Mortar: Pros and Cons

Pros

Ties directly to a manufacturer's published yield figure rather than an assumed coverage rate
Handles both blocks and bricks in one tool, since they use very different bags-per-unit figures
Useful standalone when you already have a unit count from elsewhere, without needing to re-enter wall dimensions

Cons

Assumes standard 8x8x16 block or standard brick dimensions and a typical mortar joint. A different unit size or an unusually thick or thin joint changes the actual coverage
A different mortar product (or Type S/M mortar with different sand proportions) may publish a different yield than the QUIKRETE figures used here
For a full wall material list including the blocks themselves, see the Concrete Block calculator. This tool covers mortar only

Block Mortar: What a Pro Checks

Order mortar by the unit type you're actually laying, not one flat figure. QUIKRETE's data sheet states one 80 lb bag lays up to 13 standard blocks, but the same bag covers up to 37 bricks.
Bump the waste allowance above the default 10% for a first DIY attempt or a job with a lot of cutting and patching. Mortar lost to spillage, over-buttering, and tooled-off squeeze-out adds up faster than it looks.
Mortar type (N, S, or M) changes strength and lime/cement proportions per ASTM C270, not how much volume fills the same joints, so switching type won't change the bag count this calculator gives you.

Frequently Asked Questions

How many blocks will one bag of mortar mix lay?

Up to 13 standard 8x8x16 concrete blocks per 80 lb bag, per QUIKRETE's Mortar Mix data sheet. Actual coverage can run a bit lower in practice depending on joint thickness and how much is lost to spillage, which is why this calculator applies a waste allowance on top of the manufacturer figure.

How many bricks will one bag of mortar mix lay?

Up to 37 standard bricks per 80 lb bag, per the same QUIKRETE data sheet. Bricks use far less mortar per unit than blocks since they're smaller and have thinner joints relative to their size.

What's the difference between this and the Concrete Block calculator?

The Concrete Block calculator computes both the block count (from wall dimensions) and the mortar needed together, as a single wall takeoff. This calculator skips the block-count step and just converts a unit count you already know into a mortar bag count. It's useful when you're pricing mortar separately or already have a block or brick quantity from elsewhere.

Why is the default waste allowance 10%?

Mortar is lost to spillage during mixing and placement, over-buttering joints, and squeeze-out that gets tooled off and discarded. There's no single industry-wide standard percentage for this the way there is for ready-mix ordering, so 10% is a practical planning assumption. Use less for an experienced mason working efficiently, more for a first DIY attempt or a lot of cutting and patching.

Does mortar type (N, S, M) change how many bags I need?

Not significantly for material quantity. Mortar type refers to the compressive strength and lime/cement proportions (per ASTM C270), which affects which type is appropriate for your application, not materially how much volume it takes to fill the same joints. The yield figures here are based on QUIKRETE's standard (Type N) Mortar Mix product specifically, though.

Sources

QUIKRETE Mortar Mix No. 1102 Data Sheet (yield: 13 blocks or 37 bricks per 80 lb bag) (opens in a new tab)

Concrete & Masonry