Mortar Calculator
Work out mortar bags for laying block or brick — enter your wall size, unit type and joint thickness to get bags, volume and cost.
Deducted from gross wall area. Leave 0 if none.
Net block count from your takeoff, before waste.
Face-shell is standard for hollow CMU. Full bedding uses ~60% more.
Collar joints between wythes not included.
3/8 in (0.375) is standard.
Block already includes ~10% per NCMA — consider a lower value.
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Joint thickness impact
3/8 in is your baseline
Mortar type reference
1,800 PSI
Type S — load-bearing, below grade
Sand for site-mixing
14.3 cu ft
Rule of thumb: sand ≈ mixed mortar volume
For standard 8×8×16 concrete block with a 3/8 inch face-shell joint, plan on about 8.5 cubic feet of mortar per 100 square feet of wall — roughly 22 bags of 80 lb mortar per 100 block, per NCMA-based estimating figures. For standard modular brick at the same joint size, plan on about 5.5 cubic feet per 100 square feet, close to the Brick Industry Association’s published figure of 8.1 cubic feet per 1,000 brick.
Mortar type reference
| Type | Min. strength | Typical use |
|---|---|---|
| Type M | 2,500 PSI | Below-grade, heavy loads, masonry in contact with soil |
| Type S | 1,800 PSI | Load-bearing walls, foundations, exterior work in high wind |
| Type N | 750 PSI | Above-grade exterior walls, chimneys, most residential veneer |
| Type O | 350 PSI | Interior, non-load-bearing, historic soft-brick repointing |
Per ASTM C270. Bag yield is assumed similar across types for estimating purposes — always confirm with the product you buy.
Mortar per 100 block or 1,000 brick
| Unit | Per unit | Cubic feet / 100 sf | 80 lb bags / 100 sf |
|---|---|---|---|
| 8×8×16 block, face-shell | 1.125 block/sf | 8.5 | 13 |
| 8×8×16 block, full bedding | 1.125 block/sf | 13.6 | 21 |
| Modular brick | 6.86 brick/sf | 5.5 | 9 |
| Norman brick | 4.57 brick/sf | 5.1 | 8 |
| Utility brick | 3.00 brick/sf | 3.7 | 6 |
How to calculate mortar
Block mortar is estimated from a published rate; brick mortar is calculated from the unit’s actual geometry.
- Find net wall area. Length × height, minus openings.
- Pick your unit and joint size. This is the single biggest factor in the result.
- Apply the rate. Block uses NCMA’s published 8.5 cu ft/100 sf baseline; brick is calculated directly from the brick’s specified dimensions and joint thickness.
- Add waste, then divide by bag yield and round up.
Worked examples
Block: a 20 ft long, 8 ft tall wall of standard block, 3/8 in face-shell joint:
- Net area20 × 8 = 160 sq ft
- Rate8.5 cu ft / 100 sf
- Raw volume1.60 × 8.5 = 13.6 cu ft
- Plus 5% extra waste14.3 cu ft
- Divide by 0.67 cu ft/bag14.3 ÷ 0.67 = 21.3
- Round up22 × 80 lb bags
Brick: the same 160 sf wall in modular brick, single wythe, 3/8 in joint needs about 8.9 cu ft raw, or roughly 15 bags of 80 lb mortar after waste — noticeably less than block, since brick joints are thinner and the units pack tighter.
Face-shell vs. full bedding
Most hollow concrete block is laid with face-shell bedding — mortar only on the outer webs, not across the full block width. This is standard for typical residential and light commercial walls. Full bedding, mortaring the entire top surface including cross-webs, is required for some structural and below-grade applications and uses roughly 60% more mortar for the same wall.
Common mistakes
- Using a block rule of thumb for brickBrick joints are thinner and units pack differently — a block-based rate will overestimate brick mortar significantly.
- Ignoring joint thicknessMortar volume scales roughly linearly with joint size. A 1/2 in joint instead of 3/8 in adds about a third more material.
- Forgetting full bedding requirementsSome structural and below-grade block work requires full bedding, not face-shell — check your specification before ordering face-shell quantities.
- Mixing up mortar and groutMortar bonds units together in the joints. Grout fills hollow cores. They’re different products with different consistencies and different calculators.
- Wrong mortar type for the jobType M’s rigidity can crack softer or historic brick. Type O is too weak for load-bearing work. Match the type to the application.
- Ordering the bare minimumRound up, then keep a spare bag. Running out mid-course means a visible cold joint in the coursing.
What this calculator assumes
Adjust your result if your project differs from these.
- Block: NCMA-based rate of 8.5 cu ft mortar per 100 sf at a 3/8 in face-shell joint, which already includes about 10% waste
- Brick: mortar volume calculated directly from each brick size’s specified dimensions and your joint thickness, cross-checked against the Brick Industry Association’s published modular-brick figure
- Standard running bond coursing; other bond patterns (Flemish, English, stack) change unit count and are not modeled
- Collar joints between multiple wythes are not included
- Bag yields of 0.67 cu ft (80 lb) and 0.45 cu ft (60 lb), similar across mortar types
- Queen and King brick dimensions vary by manufacturer — confirm with your supplier
- Prices are whatever you enter; they are not live market rates
Common questions
How many bags of mortar do I need per 100 block?
About 22 bags of 80 lb mortar mix for 100 standard 8×8×16 concrete block at a 3/8 in face-shell joint, per NCMA-based estimating figures.
How many bags of mortar per 1,000 bricks?
Around 12 to 13 bags of 80 lb mortar for 1,000 standard modular brick at a 3/8 in joint, close to the Brick Industry Association’s published engineering figure of 8.1 cu ft of mortar per 1,000 modular brick before waste.
What’s the difference between mortar and grout?
Mortar is a stiff paste used to bed and bond masonry units together in the joints. Grout is a flowable, wetter mix used to fill the hollow cores of block walls around rebar — it doesn’t bond units together.
What mortar type should I use for a block wall?
Type S is the standard choice for most load-bearing concrete block walls and below-grade work. Type N suits above-grade, non-load-bearing veneer. Type M is reserved for heavy loads and below-grade masonry in contact with soil.
How much does joint thickness affect mortar volume?
Mortar volume scales roughly linearly with joint thickness. Moving from a 3/8 in joint to a 1/2 in joint increases mortar volume by about a third.
Where do these numbers come from?
Block figures follow NCMA TEK 3-11 and TEK 4-2A. Brick figures are calculated from each unit’s specified dimensions and cross-checked against the Brick Industry Association’s Technical Note 10, which independently confirms the same modular-brick result.
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Wall
| Unit type | — |
| Net area | — |
| Unit count | — |
| Joint thickness | — |
| Mortar type | — |
| Waste allowance | — |
Volume
| Cubic feet (incl. waste) | — |
| Cubic yards | — |
Shopping list
| 80 lb bags | — |
| 60 lb bags | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Block rate from NCMA TEK 3-11/4-2A. Brick rate calculated from unit geometry and cross-checked against Brick Industry Association Technical Note 10. Confirm quantities and mortar type with your supplier before ordering.