How this mortar calculator works
Mortar is bought by the bag and estimated by coverage — how many units one bag lays. Turn the wall into units, add waste, and divide:
bags = units × (1 + waste) ÷ units per bag · 37 brick or 13 block per 80 lb bag
At the defaults — a 100 ft² brick wall, 10% waste — that is 675 bricks, or 21 bags of 80 lb mortar mix, about $152; the full chain is in the worked example below. Switch to block and the same wall drops to 10 bags, because block has less joint per square foot.
Mortar types N, S, M and O
Mortar is graded by strength, and using the right type matters more than using the most. The four, strongest to softest:
- Type N: the general-purpose, above-grade mortar for most brick and block — the default choice.
- Type S: stronger, for below-grade walls, foundations, retaining walls and anything with lateral load.
- Type M: the highest strength — heavy load, hard natural stone and paving.
- Type O: soft and low-strength — interior non-load-bearing work and tuckpointing old, soft brick.
- Pre-blended vs site-mixed: an 80 lb bag of mortar mix has the sand in it; site mixing means masonry cement plus masonry sand.
How far a bag of mortar goes
Coverage is set by the unit and the joint — bigger units mean fewer, wider joints per square foot, so a bag goes further:
- Brick: about 37 modular bricks per 80 lb bag — lots of small units, lots of joint.
- Block: about 13 concrete blocks per bag — fewer, bigger units, less joint per ft².
- Joint thickness: the standard ⅜ in joint is what these figures assume; a ½ in joint burns more mortar.
- Waste: mortar drops off the trowel and boards — 10% is normal, 15% for a first-timer.
- Pot life: mix only what you’ll place in about an hour; mortar left to stiffen and retempered loses strength.
Coverage figures are averages, and the mason’s hand moves them as much as the math does — a full, buttered joint uses more than a thin one, and a windy, hot day stiffens mortar fast and sends more to the board. Order a bag or two over the count rather than run short mid-course and watch a fresh batch set up while you wait on a supply run.
Mortar coverage, and bags by wall size
Table 1 is the coverage per unit; Table 2 runs a brick wall out to common sizes at 10% waste.
| Unit | Per ft² | Per 80 lb bag |
|---|---|---|
| Brick (modular) | 6.75 | 37 |
| Block (CMU) | 1.125 | 13 |
| Wall | Bricks | Bags |
|---|---|---|
| 40 ft² | 270 | 9 |
| 100 ft² | 675 | 21 |
| 160 ft² | 1,080 | 33 |
| 200 ft² | 1,350 | 41 |
How to estimate mortar for a wall
- Measure the wall area; total it on the square footage calculator, minus large openings.
- Pick the unit — brick or block — so the coverage is right.
- Set the waste — 10% for most jobs, 15% learning.
- Read the bags, and choose the mortar type — N above grade, S below — from the anatomy section.
- Add sand and water if you’re site-mixing, or just water for pre-blended bags.
Worked example: mortar for a 100 ft² brick wall
The default, worked line by line — a 100 ft² brick wall, 10% waste, $7.25 a bag:
with waste = 675 × 1.10 = 742.5
bags = 742.5 ÷ 37 = 20.1 → 21 bags
cost = 21 × $7.25 = $152
The same wall in block is a different story: 100 ft² is only 113 blocks, and at 13 per bag that is 10 bags — less than half the mortar, because a block covers six times the wall a brick does with far less joint. Pick the unit first; it moves the mortar more than the wall size does.
What this mortar estimate doesn’t include
The bags are the mortar; a masonry job needs more around them:
- The units. The brick or block themselves — priced on the brick and block calculators.
- Sand. Masonry sand if you site-mix instead of using pre-blended bags.
- Core-fill grout. For a reinforced block wall, a separate fluid mix — figured on the block calculator.
- Ties, reinforcement and flashing. Wall ties, joint reinforcement, weeps and flashing.
- Tools and water. Mixer, mortar boards, trowels and jointers.
Mortar FAQ
How much mortar do I need?
Multiply wall area by the units per square foot, then divide by the units a bag lays. A 100 ft² brick wall is 675 bricks, which takes 21 bags of 80 lb mortar mix with 10% waste — about $152. The same 100 ft² in block is 113 units and 10 bags, since block is bigger and there is less joint per square foot.
How many bricks does a bag of mortar lay?
About 37 standard bricks per 80 lb bag of mortar mix, per the common published coverage — and roughly 13 concrete blocks, since a block has less joint area per unit. Those are the two figures the calculator uses; thicker joints or heavy tooling use a little more.
How much mortar do I need for 100 bricks?
About 3 bags of 80 lb mortar mix — 100 bricks at 37 per bag is 2.7 bags, rounded up with a little waste. For a quick job, one bag per 35–40 bricks is the number to carry in your head; the calculator scales it to a whole wall.
What is the difference between mortar types N, S, M and O?
They are strength grades. Type N is the general-purpose above-grade mortar for most brick and block. Type S is stronger, for below-grade walls, foundations and anything taking lateral load. Type M is the strongest, for heavy load and hard stone. Type O is a soft, low-strength mortar for interior, non-load-bearing work and tuckpointing old soft brick.
How much sand and cement do I need for mortar?
Pre-blended 80 lb mortar mix already has the sand in it — just add water — which is what this calculator counts. If you site-mix, a common Type N recipe is 1 part masonry cement to about 3 parts masonry sand (or 1 part portland, 1 part lime, 6 parts sand). Figure the sand on the sand calculator once you know the bag count.
Is mortar the same as concrete or grout?
No. Mortar is the bedding that bonds brick and block, mixed stiff to hold a joint. Concrete is a structural mix with stone aggregate, poured for slabs and footings. Grout is a fluid mix that fills block cores or tile joints. They look similar in the bag but do three different jobs.
How much does a bag of mortar cost?
A pre-blended 80 lb bag of Type N or S mortar mix runs about $6 to $9 in 2026, so the default 100 ft² brick wall is around $152 at $7.25 a bag. Colored and Type S mortars cost a bit more; buying by the pallet drops the per-bag price.
Sources and standards
The coverage is estimating practice; the types are a material standard:
- ASTM C270: the mortar specification behind types N, S, M and O and their proportions.
- Published bag coverage: about 37 bricks or 13 blocks per 80 lb bag of mortar mix at ⅜ in joints.
- Matched constants: the same 6.75 brick and 1.125 block per ft² the brick and block calculators use.
- The mix on site: joint thickness, tooling and the mason’s hand move real usage — buy a little over.
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