Mortar Calculator
Work out the bags of mortar and sand needed to lay brick or block.
What you'll need to order
- type N or S mortar mix
- masonry sand
- portland cement
- hydrated lime
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
bags = number of units ÷ units per bag
Coverage varies with joint thickness and the mason. These figures assume a standard 3/8 inch joint. A sloppy hand or a thicker joint can push consumption up 20%.
Worked example
With number of units 500 , units per 70 lb bag 125 , this calculator returns 4 bags.
Mortar bags by unit count
Figures below assume units per 70 lb bag 125 . Change any measurement in the calculator to get your own numbers.
| Number of units | Mortar bags (70 lb) (bags) | Masonry sand if mixing from scratch (cu ft) | Portland cement bags (94 lb) (bags) |
|---|---|---|---|
| 100 | 0.80 | 0.54 | 0.06 |
| 250 | 2.00 | 1.35 | 0.15 |
| 500 | 4.00 | 2.70 | 0.30 |
| 1000 | 8.00 | 5.40 | 0.60 |
| 2000 | 16.00 | 10.80 | 1.20 |
| 5000 | 40.00 | 27.00 | 3.00 |
At 125 units per bag — the typical figure for modular brick with a 3/8 in joint. Concrete block lays about 28 per bag.
Mortar for common masonry jobs
| Job | Size | Mortar bags (70 lb) |
|---|---|---|
| Garden wall, 400 bricks | 400 × 125 | 3.20 bags |
| House veneer, 3,000 bricks | 3000 × 125 | 24.00 bags |
| Block garage wall, 400 blocks | 400 × 28 | 14.29 bags |
| Basement wall, 800 blocks | 800 × 28 | 28.57 bags |
| Chimney rebuild, 600 bricks | 600 × 125 | 4.80 bags |
Block uses far more mortar per unit than brick because the bed joints are much larger. Set units per bag to 28 for standard CMU.
Mortar types and where each belongs
| Type | Compressive strength (psi) | Notes |
|---|---|---|
| Type N | 750.0 | General above-grade use; the default |
| Type S | 1,800 | Below grade, retaining walls, high wind |
| Type M | 2,500 | Foundations and heavy structural masonry |
| Type O | 350.0 | Repointing soft historic brick only |
| Type K | 75.00 | Conservation work on very soft masonry |
Stronger is not better. Mortar must be weaker than the units it joins — hard modern mortar on soft old brick forces the movement into the brick face, which then spalls.
Frequently asked questions
How many bags of mortar do I need?
Divide the number of units by the coverage per bag: about 125 for modular brick, 28 for standard concrete block. A 400-brick garden wall needs roughly 4 bags.
How much sand per bag of mortar?
About 3 cubic feet of mason sand per 70 lb bag of mortar mix if you are mixing from portland and lime, or none at all if you buy premixed mortar.
What is the mix ratio for type S mortar?
One part portland cement, half a part hydrated lime, and four and a half parts sand by volume. Type N is 1 : 1 : 6.
How many bricks does one bag of mortar lay?
Around 125 modular bricks per 70 lb bag with a 3/8 inch joint. Block goes much further per square foot but only 28 blocks per bag, because each unit is larger.
Is it cheaper to mix mortar from scratch?
On a large job, yes — portland, lime and sand bought separately cost roughly half what pre-blended bags do. On anything under a few hundred units the saving is not worth the mixing time or the risk of an inconsistent batch.
What is the mix ratio for type N mortar?
One part portland cement, one part hydrated lime, six parts masonry sand by volume. Type S is richer at one part cement to half a part lime and four and a half parts sand.
How long can mixed mortar sit before use?
Two to two and a half hours in mild weather, and half that in heat. You can retemper once with a little water within that window. After it starts to stiffen from hydration rather than evaporation, discard it.