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.
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 |