Mortar Calculator - Estimate Cement, Sand & Bags for Any Masonry Job
Calculate mortar quantity for brick walls, concrete block walls, repointing joints, and mortar beds. Returns total volume in cubic feet and cubic yards, plus cement, sand, and lime weights broken out by your selected ASTM C270 mix type. Pre-mixed bag counts for 60 lb and 80 lb bags are included automatically.
🧱 Mortar Calculator
Rebar Weight Chart
US Standard Rebar Sizes (#2–#18) with Weight, Diameter & Area
View Chart →How Mortar Volume Is Calculated
Each project type uses a different formula because the geometry of mortar joints differs between brick, block, repointing, and mortar beds. The formulas below match the methods used by this calculator.
Brick Wall
V = Wall Area × Joint % × Wall Thickness
Mortar occupies roughly 17–22% of a standard 4-inch single-wythe wall with 3/8-inch joints (modular brick, 3 courses per 8 inches). Joint percentage scales with joint thickness and brick size.
Source: Brick Industry Association Technical Note 8 (2020)
Concrete Block Wall
V = (Wall Area / Block Face Area) × Joint Volume per Block
For a standard 8×8×16 CMU with face-shell bedding, mortar volume per block is approximately 0.057 ft³. Full bedding adds about 60% more mortar per block. Source: ASTM C90-22.
Source: ASTM C90-22, NCMA TEK 3-6B
Repointing
V = Joint Length × Joint Width × Rake Depth
Joint linear footage per ft² of wall face is estimated from brick coursing geometry (roughly 15–18 LF/ft² for standard brick). Rake depth is the new mortar fill depth after removing deteriorated mortar.
Source: ASTM C1634-15, BIA Technical Note 46
Mortar Bed
V = Length × Width × Thickness
Simple rectangular volume for thick-set mud-bed installations. Per TCNA Handbook Method F115, floor mortar beds run 1-1/4 to 1-1/2 inches. Shower pan beds slope to 1/4 inch per foot toward the drain.
Source: TCNA Handbook F115, TR712 (2024 Ed.)
ASTM C270 Mix Ratios by Type
The mix ratio determines how much cement, lime, and sand go into each cubic foot of mortar. This calculator uses proportion specifications per ASTM C270-24 Table 1.
| Mortar Type | Cement : Lime : Sand | Min Compressive Strength | Water Retention | Primary Use |
|---|---|---|---|---|
| Type M | 1 : 1/4 : 3 | 2,500 PSI | 70% | Foundations, retaining walls, below-grade |
| Type S | 1 : 1/2 : 4.5 | 1,800 PSI | 75% | Load-bearing walls, below-grade, severe exposure |
| Type N ✓ | 1 : 1 : 6 | 750 PSI | 75% | Above-grade walls, chimneys, general residential |
| Type O | 1 : 2 : 9 | 350 PSI | 70% | Interior non-load-bearing, low-stress applications |
Data from ASTM C270-24, Table 1 (Proportion Specification). ✓ = default selection for general residential work.
Mortar Coverage Quick Reference
These planning values are commonly used in the field and are consistent with BIA and NCMA technical literature. Use as starting estimates before running the full calculation above.
Brick Masonry Coverage
| Brick Type | Joint | Mortar / 100 ft² | Bags (60 lb) / 100 ft² |
|---|---|---|---|
| Modular (3-5/8 × 2-1/4 × 7-5/8 in) | 3/8 in | 6.0 – 6.8 ft³ | 13 – 16 |
| Standard (3-3/4 × 2-1/4 × 8 in) | 3/8 in | 6.5 – 7.0 ft³ | 14 – 16 |
| Utility (3-5/8 × 3-5/8 × 11-5/8 in) | 3/8 in | 4.5 – 5.2 ft³ | 10 – 12 |
| Any brick | 1/4 in | ~4.0 ft³ | 9 – 10 |
| Any brick | 1/2 in | ~8.2 ft³ | 18 – 20 |
Source: BIA Technical Note 8 (2020). Values are for single-wythe 4-inch walls.
CMU Block Coverage
| Block Size | Bedding | Mortar / 100 ft² | Bags (60 lb) / 100 ft² |
|---|---|---|---|
| 8×8×16 in standard | Face shell | 3.5 – 4.0 ft³ | 8 – 9 |
| 8×8×16 in standard | Full bed | 5.5 – 6.5 ft³ | 12 – 15 |
| 6×8×16 in CMU | Face shell | 3.0 – 3.5 ft³ | 7 – 8 |
| 12×8×16 in CMU | Face shell | 4.0 – 4.8 ft³ | 9 – 11 |
Source: NCMA TEK 3-6B. Values per 100 ft² of wall face area.
Mortar Types, Materials, and Mix Selection
Mortar is not a single product. The four types defined in ASTM C270 differ in compressive strength, flexibility, and weather resistance. Selecting the wrong type is one of the most common and costly masonry mistakes on residential projects.
When to Use Each Mortar Type
🔴 Type M — Maximum Strength
2,500+ PSI. Required for masonry in contact with soil (foundation walls, retaining walls, piers) and for applications exposed to freeze-thaw cycles below grade. Its rigidity can crack softer brick units, so avoid on historic or soft-fired brick.
🟠 Type S — Structural Exterior
1,800 PSI. Specified for load-bearing walls, masonry below grade that may contact soil, and exterior work subject to wind loads greater than 80 mph. The standard for most new-construction exterior walls in the Southeast and Gulf Coast.
🟢 Type N — General Purpose
750 PSI. The most widely used mortar in residential construction. Appropriate for above-grade exterior walls, chimneys, and veneers not subject to high lateral loads. Its higher lime content improves workability and bond in hot weather.
🔵 Type O — Interior / Light Use
350 PSI. Limited to interior, non-load-bearing partitions and areas not exposed to freezing temperatures. Sometimes used for repointing historic soft brick where a weaker, more flexible mortar is needed to prevent spalling adjacent units.
The Role of Lime in Masonry Mortar
Hydrated lime (ASTM C207 Type S) is the third ingredient in most ASTM C270 mortars. It improves water retention during hot or windy curing conditions, increases workability, reduces shrinkage cracking, and promotes autogenous self-healing of hairline cracks over time. See the water-cement ratio calculator for related cement-water science.
Lime-free mortars (sometimes labeled "masonry cement mortars" per ASTM C91) use air-entrainment as a plasticizer substitute and generally fall under a different specification. This calculator uses ASTM C270 proportion mixes with lime. If your product is a masonry cement mortar, bag yield may differ from the values shown here.
Site-Mixed vs. Pre-Mixed Bags
Pre-mixed bags (Portland cement + lime + sand pre-blended) cost 30–50% more per cubic foot than site-mixed materials but eliminate batching errors. For projects under 5 cubic yards, pre-mixed bags are cost-effective. For larger projects, buying materials separately and using the mix ratios from this calculator's results saves significant money. The concrete mix ratio calculator applies the same principle to concrete batching.
Sample Calculations
Residential Garden Wall, 20 ft × 6 ft, Type N
Dimensions: 20 ft × 6 ft = 120 ft² wall face
Wall type: Single wythe (4 in), standard modular brick
Joint: 3/8 in standard, 10% waste factor
Mortar type: Type N (1:1:6, cement:lime:sand)
Mortar fraction for 4-in wall, 3/8-in joints ≈ 0.20 (20%)
Gross mortar volume = 120 ft² × 0.333 ft × 0.20 = 8.0 ft³
+ 10% waste = 8.0 × 1.10 = 8.8 ft³
Type N ratio (1:1:6 by volume): 8 parts total
Cement = 8.8 / 8 × 1 = 1.1 ft³ → 2 bags (94 lb)
Lime = 8.8 / 8 × 1 = 1.1 ft³ → 1 bag (50 lb)
Sand = 8.8 / 8 × 6 = 6.6 ft³ → ~550 lb
60 lb pre-mixed bags = 8.8 ÷ 0.45 = 20 bags
At $8.50/bag, pre-mixed cost is ~$170. Site-mixed material cost is approximately $60–$75. For a 120 ft² wall, site-mixing saves about $100 but requires 30 minutes of additional batching time.
8×8×16 CMU Retaining Wall, 40 ft × 4 ft, Type S
Dimensions: 40 ft × 4 ft = 160 ft² wall face
Block: Standard 8×8×16 CMU, face-shell bedding
Mortar type: Type S (1:0.5:4.5) — required for retaining wall per IBC §2104
Waste: 10%
Block face area = (16 in × 8 in) / 144 = 0.889 ft²
Number of blocks = 160 / 0.889 = 180 blocks
Mortar per block (face shell) ≈ 0.057 ft³
Net mortar = 180 × 0.057 = 10.26 ft³
+ 10% waste = 10.26 × 1.10 = 11.3 ft³
60 lb bags = 11.3 ÷ 0.45 = 26 bags
The load-bearing retaining wall specification requires Type S, not Type N. Substituting Type N on a below-grade retaining wall does not meet IBC §2104 and can fail inspection.
Chimney Repoint, 80 ft² of Exterior Brick, Type S
Area: 80 ft² chimney face
Joint width: 3/8 in, rake depth 3/4 in
Masonry: Standard modular brick
Waste: 15% (repointing work)
Joint LF per ft² (modular brick, 3/8 in) ≈ 16 LF/ft²
Total joint LF = 80 × 16 = 1,280 LF
Joint width = 0.375 in ÷ 12 = 0.03125 ft
Rake depth = 0.75 in ÷ 12 = 0.0625 ft
Net mortar = 1,280 × 0.03125 × 0.0625 = 2.5 ft³
+ 15% waste = 2.5 × 1.15 = 2.88 ft³
60 lb bags = 2.88 ÷ 0.45 = 7 bags
For chimneys above the roofline, Type S is specified per most local codes due to exposure to severe weather and freeze-thaw cycling. Using Type N on an exterior chimney stack in climates with more than 25 freeze-thaw cycles per year accelerates joint deterioration.
Field Errors That Lead to Failed Mortar Joints
These mistakes appear repeatedly in mortar project callbacks and warranty claims. Each one is preventable with the correct specification and mixing practice.
⚠️ Error 1 — Using Type M Mortar on Old or Soft Brick
Pre-1940 brick was often fired at lower temperatures and has lower compressive strength than modern brick. Installing Type M mortar (2,500 PSI) against soft brick creates a differential: the joint is harder than the masonry unit. Freeze-thaw expansion then spalls the brick face, not the joint. ASTM C270 warns that mortar should be no stronger than the masonry unit it bonds. For historic brick, Type O or a custom lime mortar is often the correct specification.
⚠️ Error 2 — Batching Mortar by Weight Instead of Volume
ASTM C270 proportion specifications are by volume, not weight. Measuring 1 shovel of cement to 6 shovels of sand is a reasonable approximation, but weighing materials without volumetric adjustment introduces errors because sand bulk density varies with moisture content (dry sand at 100 lb/ft³ vs. damp sand at 120 lb/ft³). Always batch by volume using a consistent container. See the concrete mix calculator for Portland cement batching by volume.
⚠️ Error 3 — Adding Too Much Water to Extend Working Time
Adding water to stiffening mortar (re-tempering) is permitted only within the first 2.5 hours and before final set, per ASTM C270 and ACI 530.1. Excessive water reduces compressive strength by the water-cement ratio effect: a 10% excess water addition reduces 28-day strength by approximately 15–20% (ACI 318-19 §26.4). Discard mortar that has been in the mixer for more than 2.5 hours or has stiffened beyond re-tempering.
⚠️ Error 4 — Estimating Mortar from Brick Count Alone
A common rule-of-thumb is 1 bag of mortar per 25–30 bricks. This approximation works only for standard modular brick at 3/8-inch joints with 10% waste. It fails for utility brick (fewer joints per ft²), oversize brick, thick joints over 1/2 inch, or double-wythe walls. Always calculate from wall dimensions and joint geometry using this calculator to avoid ordering shortfalls or excess.
⚠️ Error 5 — Not Adjusting Waste for Repointing vs. New Work
New brickwork waste of 10% is standard. Repointing waste should be 15–20% because rake depth varies across weathered joints, mortar falls during application, and joint widths are rarely uniform after years of exposure. Under-ordering repointing mortar for an exterior chimney or parapet wall forces a second delivery, delays the project, and risks color variation between batches if bags are from different production lots.
Mortar Specification by Application and Code Requirements
IBC and IRC Mortar Type Requirements
The International Building Code (IBC 2024 §2104.2) and International Residential Code (IRC 2021 §R607) specify minimum mortar types by application. Substituting a weaker type will not pass inspection on permitted work.
| Application | Min Mortar Type | Code Reference | Notes |
|---|---|---|---|
| Foundation walls, below grade | Type M or S | IBC §2104.2 | Type M preferred where in contact with soil |
| Exterior load-bearing walls | Type S or N | IBC §2104.2 | Type S for seismic/high-wind zones |
| Chimneys (above roofline) | Type S | IRC §R1003.9 | Exposed to severe freeze-thaw |
| Above-grade non-structural | Type N | IBC §2104.2 | Standard for residential veneer |
| Interior non-load-bearing | Type O | IBC §2104.2 | Not for exterior or freeze-thaw exposure |
| Masonry veneer over wood frame | Type S or N | IBC §1405.6 | ASTM C270 required, lime content important for bond |
Always confirm requirements with your local building department. Seismic Design Categories D, E, F may require Type S in applications where Type N is listed above.
Ordering Pre-Mixed Mortar Bags
Pre-mixed mortar bags are available in Type N (most stocked), Type S, and Type M at major home improvement retailers. Type O is less commonly stocked and may require special order. Bag yield stated on the label is achieved only with proper water addition — most products specify a water-to-bag ratio. Using less water to achieve "stiffer" mortar reduces workability and yield. The ready-mix bag calculator applies the same bag-yield logic to concrete bags.
Curing and Working Time
Mortar working time is 2.5 hours from initial water addition at 70°F per ASTM C270. In temperatures above 90°F or with wind speed over 15 mph, working time drops to 60–90 minutes. In temperatures below 40°F, cold-weather masonry practices per ASTM C1072 apply: pre-heat mixing water to 70–140°F and protect completed work from freezing for at least 24 hours. For related mixing guidance, see the concrete mixing instructions page.
Frequently Asked Questions
-
How much mortar do I need per square foot of brick wall?
A standard 4-inch single-wythe brick wall with 3/8-inch joints requires approximately 6.0 to 6.8 cubic feet of mortar per 100 square feet of wall face (0.06 to 0.068 ft³ per ft²). That equals roughly 14 to 16 bags of 60 lb pre-mixed mortar per 100 ft². Values increase proportionally for thicker walls or wider joints. Source: BIA Technical Note 8 (2020).
-
What is the difference between Type S and Type N mortar?
Type S has a minimum compressive strength of 1,800 PSI versus 750 PSI for Type N per ASTM C270-24. The mix ratio also differs: Type S is 1:0.5:4.5 (cement:lime:sand) while Type N is 1:1:6. Type S is required for load-bearing walls, below-grade masonry, chimneys above the roofline, and high-wind or seismic zones. Type N is appropriate for above-grade, non-structural exterior walls and general residential brickwork. If in doubt, use Type S — it is always acceptable where Type N is specified, but not vice versa.
-
How many bags of mortar do I need for 100 concrete blocks?
For standard 8×8×16 CMU blocks with face-shell bedding and 3/8-inch joints, plan on approximately 0.057 cubic feet of mortar per block. For 100 blocks: 100 × 0.057 = 5.7 ft³ net, plus 10% waste = 6.3 ft³. At 0.45 ft³ yield per 60 lb bag, you need 14 bags. At 0.67 ft³ yield per 80 lb bag, you need 10 bags. Full bedding adds roughly 60% more mortar — use 22 bags (60 lb) for 100 blocks with full bedding. Source: NCMA TEK 3-6B.
-
Can I use the same mortar for repointing that I use for new brickwork?
Not always. For modern hard brick (fired after 1960), yes — Type N or Type S new-work mortar is appropriate for repointing the same masonry type. For pre-1940 or historic soft brick, the repointing mortar must be softer and more flexible than the masonry unit. ASTM C270 Type O or a natural hydraulic lime mortar (NHL) is often specified to avoid spalling. See the Secretary of the Interior's Standards for Historic Preservation, Preservation Brief 2 (2016 update) for detailed guidance on matching historic mortars.
-
How thick should my mortar bed be for floor tile?
Per TCNA Handbook Method F115 (2024 Edition), standard floor mortar beds for ceramic and porcelain tile should be 1-1/4 to 1-1/2 inches thick, reinforced with wire mesh. For shower pan floors, the mud bed must be sloped 1/4 inch per foot toward the drain and typically ranges from 1-1/4 inches at the walls to 2-3/4 inches at the low point near the drain. The mortar mix for mud beds is Portland cement, sand, and water only (no lime) — typically a 1:4 or 1:5 ratio by volume.
-
How do I calculate the cement and sand quantities from mortar volume?
Divide total mortar volume by the sum of mix ratio parts, then multiply by each material's ratio. For Type N (1:1:6 = 8 total parts): if you need 10 ft³ of mortar, cement = 10 ÷ 8 × 1 = 1.25 ft³ (about 2 bags of 94 lb Portland cement at ~0.67 ft³/bag), lime = 1.25 ft³ (about 1.5 bags of 50 lb hydrated lime at ~0.8 ft³/bag), sand = 10 ÷ 8 × 6 = 7.5 ft³ (about 625 lb at 100 lb/ft³ dry). The calculator above does this breakdown automatically for all four ASTM C270 mortar types. Compare this to 1:2:4 concrete mix ratios for a concrete mixing parallel.
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How long does mortar take to cure?
Mortar reaches initial set in 2 to 4 hours under standard conditions (70°F, moderate humidity). Sufficient strength for light foot traffic on mortar-bed floors is achieved in 24 to 48 hours. Full compressive strength develops over 28 days, the same timeline as concrete per ACI 318-19. In temperatures below 50°F, curing slows significantly and can stop below 40°F without cold-weather protection. Mortar joints should not be wetted, disturbed, or loaded during the first 24 hours. For related curing data see the concrete curing and finishing guide.
Sources & Calculation Methodology
All formulas, mix ratios, and reference data in this calculator are drawn from published engineering standards and manufacturer technical documentation. No values are approximated without citation.
- ASTM C270-24 — Standard Specification for Mortar for Unit Masonry. ASTM International, 2024. Table 1 (Proportion Specifications) and Table 2 (Property Specifications) used for all Type M, S, N, O mix ratios and strength values. ASTM C270 →
- BIA Technical Note 8 (2020) — Mortars for Brickwork. Brick Industry Association. Mortar coverage values per 100 ft² of brick wall, joint percentage factors, and waste factor guidance. BIA Technical Notes →
- NCMA TEK 3-6B — Mortar for Concrete Masonry. National Concrete Masonry Association. CMU mortar volume per block for face-shell and full bedding; data used in block-wall calculations. NCMA TEK 3-6B →
- TCNA Handbook Method F115 (2024 Edition) — Mortar Bed Floor Installation. Tile Council of North America. Mortar bed thickness standards (1-1/4 to 1-1/2 in for floors, up to 2-3/4 in for shower drains) used in mortar bed calculations. TCNA Standards →
- ASTM C1634-15 — Standard Practice for Cold Weather Masonry Construction. Cited for repointing rake depth standard (3/4 in minimum) and cold-weather working time limits. Also referenced: BIA Technical Note 46.
- IBC 2024 §2104.2 — International Building Code 2024, Chapter 21, Masonry. Minimum mortar type requirements by application. Used in the application-context table. IBC 2024 →
- Quikrete / Sakrete Technical Data Sheets — Mortar Mix product TDS. Bag yield values: 60 lb bag = 0.45 ft³, 80 lb bag = 0.67 ft³. Used in bag count calculations. Quikrete Mortar TDS →
Reviewed by site author — Muhammad Ramzan Babar, Physics Researcher (PhD Candidate). Last reviewed: June 2026. All calculations run in your browser. No project data is transmitted or stored.
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