Mortar Calculator
Estimate mortar for brick and block: bags of premixed mortar, or masonry cement and sand, by unit count or wall area. Includes Type N, S, M, O mix ratios per ASTM C270. Free, no sign-up.
What to calculate next
Tools commonly used alongside this calculation
Concrete Block (CMU) Calculator
Estimate a CMU wall from its size: block count, mortar (cement + sand), core-fill grout, and rebar for 6, 8, and 12 in units per NCMA TEK 14-13. Subtract openings and add a waste allowance. Free, no sign-up.
Concrete Calculator
Calculate concrete for slabs, footings, walls, columns, and sonotubes. Add pours to get total cubic yards, the number of 40/60/80 lb bags, a waste allowance, and ready-mix cost. Free, no sign-up.
Rebar Weight Calculator
Calculate rebar weight from ASTM A615 bar sizes. Add bars by size, length, and quantity to get the total weight in pounds and tons, plus a per-bar breakdown and optional cost. Free, no sign-up.
Explanation
Mortar is sold two ways: as premixed bags you just add water to, or as masonry cement mixed with your own sand. Either way the question is the same — how many bags do I need to lay this much brick or block? This calculator answers it from a unit count or a wall area, for CMU block and the common brick sizes, and shows the Type N, S, M, and O mix proportions so you pick the right mortar for the job.
How much mortar a wall takes
Mortar is estimated from the number of units. If you only know the wall size, the count comes from the units per square foot first, then the bag count follows from how many units one bag lays with a standard 3⁄8 in joint:
If you mix your own, plan on three bags of masonry cement per 100 block (about one bag per 33 block) with roughly one cubic yard of sand per seven bags of cement. The same wall take-off pairs naturally with the concrete block calculator, which totals the blocks, grout, and rebar for a CMU wall on one screen.
| Unit | Per ft² | Per 80 lb bag | Per cement bag |
|---|---|---|---|
| CMU block (8×8×16) | 1.125 | 12 | 33 |
| Modular brick | 7 | 33 | 142 |
| Standard brick | 6.5 | 30 | 125 |
| Queen brick | 6 | 28 | 125 |
| Utility brick | 3 | 20 | 100 |
Mortar types N, S, M, and O
Mortar type is a strength class, not a quantity. Under the ASTM C270 proportion specification each type is a ratio by volume of portland cement to hydrated lime to sand — more cement and less lime gives a stronger, less workable mortar. Premixed masonry cement is sold pre-blended as Type N, S, or M, so you choose the type at the store; the number of bags does not change.
| Type | Cement : Lime : Sand | Min. psi | Typical use |
|---|---|---|---|
| Type M | 1 : ¼ : 3 | 2,500 | Foundations, retaining walls, below grade |
| Type S | 1 : ½ : 4½ | 1,800 | Structural and at-grade walls, high wind/seismic |
| Type N | 1 : 1 : 6 | 750 | General-purpose above-grade walls, chimneys |
| Type O | 1 : 2 : 9 | 350 | Interior, non-load-bearing, repointing |
Type N is the everyday choice for above-grade brick and block. Step up to Type S at or below grade and where wind or seismic loads are high, and to Type M for foundations and retaining walls. A structural wall’s mortar type, reinforcement, and grouting are set by the engineer of record — the same drawings that drive your rebar weight take-off.
Notes and assumptions
Coverage figures assume nominal units and a 3⁄8 in joint. Real yield swings with joint thickness, brick texture, waste, and how full the head and bed joints are struck, so treat the bag count as an ordering estimate and round up. Slick joints and partial-bed work use less; deep raked or buttered joints use more.
Premixed mortar and masonry cement are not the same product as the grout and ready-mix poured into footings or filled cells — that material is sized with the concrete calculator. Keep at least one spare bag on site so the last course is never short, and store unopened bags dry — cement that has taken on moisture will not gain full strength.