How much mortar do I need?
Estimate the number of 60-lb bags of mortar for brick or concrete block projects based on the number of units.
Mortar calculator
Choosing the Right Mortar Type
Mortar type determines the strength, flexibility, and weather resistance of your masonry project. Using the wrong type can lead to cracked joints or structural failure.
Type N Mortar: A general-purpose mortar with medium strength (750 psi). Ideal for above-grade exterior walls, veneers, and interior partitions. Type N offers good flexibility and weather resistance for most residential projects.
Type S Mortar: High-strength mortar (1800 psi) designed for below-grade applications, retaining walls, foundations, and manholes. Type S resists soil pressure and moisture better than Type N.
Type M Mortar: The highest strength (2500 psi) mortar, used for heavy-load applications like retaining walls, foundations, and pavements. Less flexible than Type S, so it is not recommended for thin joints or veneers.
Type O Mortar: Low-strength mortar (350 psi) used for interior non-load-bearing walls and repointing historic structures where softer, more breathable mortar is needed to match original materials.
Mortar Type Cheat Sheet
Use this reference to select the right mortar for your project:
| Type | Strength (psi) | Best Used For |
|---|---|---|
| Type N | 750 | Above-grade walls, veneers, chimneys, interior partitions |
| Type S | 1800 | Below-grade walls, retaining walls, foundations, manholes |
| Type M | 2500 | Heavy-load walls, foundations, retaining walls, pavements |
| Type O | 350 | Interior non-load-bearing walls, historic repointing |
Mortar mixing tips
Use a mortar mixing paddle and bucket for small batches. Add water gradually while mixing until the mortar reaches a peanut butter consistency. Mortar has a working time of about 2-3 hours, so mix only what you can use in that time. Keep mortar from freezing for 24-48 hours after application.
How to estimate mortar
Mortar estimation depends on the type of unit you're laying. Bricks use less mortar per unit than blocks, but the total depends on wall area, joint thickness, and waste. Standard mortar joints are ⅜ inch for brick and ⅜-½ inch for block. Calculate the total wall area in square feet, then use the coverage rates: roughly 0.02 cu ft per brick or 0.38 cu ft per 8×8×16 block. Add 10-15% waste for cutting, spillage, and mixing losses.
- Brick walls: about 3 bags of mortar per 100 bricks (60-lb bags)
- Block walls: about 1.5 bags of mortar per 100 blocks (80-lb bags)
- Thin brick veneer: uses about half the mortar of full-depth brick
Mortar types explained
ASTM mortar types are designated by letters: N, S, M, and O. Type N is the most common for general use — it's a middle-strength mortar suitable for above-grade walls and interior projects. Type S is stronger and used for structural applications, retaining walls, and below-grade work. Type M is the strongest and used for foundations and high-load applications. Type O is the weakest, only for interior non-load-bearing walls.
- Type N: 750 psi compressive strength — general purpose, above-grade walls
- Type S: 1,800 psi — structural, below-grade, retaining walls
- Type M: 2,500 psi — heavy loads, foundations, high-traffic areas
- Type O: 350 psi — interior, non-load-bearing only
Mixing mortar properly
Add water to the mortar mix gradually — you want a smooth, peanut-butter-like consistency that holds its shape on a trowel without slumping. Mix for 3-5 minutes after all dry material is wet. Let the mixed mortar slake (rest) for 5-10 minutes, then remix briefly before use. This allows the chemicals to fully activate. Never add water to mortar that has started to set, and don't mix more than you can use in 2-2.5 hours.
- Water ratio: roughly 6 quarts per 80-lb bag; adjust for humidity and temperature
- Tool: use a drill-mounted paddle mixer for consistent results — hand mixing is unreliable
- Cleanup: wash tools before mortar hardens; it's much harder to remove once set
Worked example
For example, for 500 bricks, using Type S mortar:
- 500 bricks × 0.02 cu ft per brick = 10 cu ft of mortar
- 60-lb bags: 10 ÷ 0.75 = 13.3 → 14 bags needed
- For blocks: 500 blocks × 0.38 cu ft = 190 cu ft → 254 bags
- Add 1-2 extra bags for waste and buttering
Common mistakes
| Mistake | Why it matters |
|---|---|
| Mixing too much at once | Mortar sets in 1.5-2.5 hours — only mix what you can use in that time |
| Using the wrong mortar type | Type N for above-grade walls, Type S for below-grade or retaining walls |
| Adding too much water | Stiff mortar holds brick in place — wet mortar causes bricks to slide out of alignment |
Frequently asked questions about mortar estimates
How many bags of mortar do I need per 100 bricks?
You need approximately 2 to 3 bags of 60-lb mortar mix per 100 standard bricks, depending on joint thickness and application method.
What is the difference between Type N and Type S mortar?
Type N is a general-purpose mortar for above-grade walls with medium strength (750 psi). Type S is high-strength (1800 psi) for below-grade and retaining wall applications.
How long does mortar take to set?
Mortar begins to set in 1.5 to 2.5 hours and reaches full strength after 28 days. Do not disturb freshly laid masonry for at least 24 hours.