How much mortar does a bag make?

It depends on the product. A bag of masonry cement is mixed with sand on site (about 3 bags of cement per 100 block, plus the sand); a bag of pre-mixed mortar has the sand already in it and runs about 7.5 per 100 block. Joint thickness moves both, so confirm the coverage on your bag.

Block vs brick — does the mortar change?

Mostly through the unit count: a square foot of wall is about 1.125 blocks but about 6.55 modular bricks (at a standard 3/8-inch joint), so brick has far more joint and uses more mortar per square foot. Set the unit type and adjust the bags-per-100 to your mortar.

If you use masonry or Portland cement, yes — it's mixed with sand on site (commonly around 1 part cement to 3 parts sand). Pre-mixed mortar already includes the sand; just add water.

Mortar Calculator

Enter the wall area and whether you're laying block or brick, and this estimates the bags of mortar — with the bags-per-100 figure left editable, since it varies by mortar type and joint.

Mortar bags

4bags

Units (brick/block): 113 units

How these numbers are worked out

The formula

Units = wall area × units per square foot (about 1.125 for standard 8×8×16 block, 6.55 for modular brick at a 3/8-inch joint). Bags = units ÷ 100 × bags per 100, rounded up. The bags-per-100 figure depends on the mortar and joint, so it's an input — masonry cement mixed with sand runs about 3 bags per 100 units, pre-mixed mortar about 7.5.

Constants and sources

Units = area × units/sq ft (block ≈1.125; modular brick ≈6.55 at a 3/8-in joint, per the Brick Industry Association — geometric conventions). Bags = units ÷ 100 × bags/100; bags/100 is product-dependent (≈3 masonry cement + sand, ≈7.5 pre-mix) — entered, verify on the bag.

How it was checked

Last reviewed June 16, 2026. Before this calculator was published, its formula, constants and worked example were checked in a separate, AI-assisted review that redid the arithmetic and tested the factual claims; the site owner then approved it for publishing. No engineer or tradesperson reviews these pages. Where a figure depends on the product (a density, a coverage rate, a bag size), it is either an input you can change above or a fixed planning value stated on this page, so check it against your product's label or your supplier.

Spot a wrong number or an outdated figure? Send a correction.

Worked example

100 sq ft of 8×8×16 block ≈ 113 blocks. At 3 bags per 100 (masonry cement + sand): ⌈113 ÷ 100 × 3⌉ = 4 bags, plus the sand to mix with it.

FAQs

How much mortar does a bag make?: It depends on the product. A bag of masonry cement is mixed with sand on site (about 3 bags of cement per 100 block, plus the sand); a bag of pre-mixed mortar has the sand already in it and runs about 7.5 per 100 block. Joint thickness moves both, so confirm the coverage on your bag.
Block vs brick — does the mortar change?: Mostly through the unit count: a square foot of wall is about 1.125 blocks but about 6.55 modular bricks (at a standard 3/8-inch joint), so brick has far more joint and uses more mortar per square foot. Set the unit type and adjust the bags-per-100 to your mortar.
Do I need sand too?: If you use masonry or Portland cement, yes — it's mixed with sand on site (commonly around 1 part cement to 3 parts sand). Pre-mixed mortar already includes the sand; just add water.