Mortar calculator
Estimate how much mortar you need for brick, block, or stone masonry — get cement, sand, lime, and pre-mixed bag quantities based on ASTM C270 mix ratios.
Inputs
Masonry unit
Results
Pre-mixed bags (80 lb / ~36 kg)
Enter your measurements to see the result
bags
Mortar volume (wet)
—
litres
Wall area
—
m²
Cement
—
× 25 kg bags
Sand
—
kg
Lime
—
m³ hydrated lime
⚠ Type N mix ratio 1:1:6 (cement:lime:sand) — 750 psi lab-tested minimum (ASTM C270 property spec); BIA-recommended for above-grade veneer, chimneys, non-loadbearing and interior walls. Includes 10% waste and a 1.3 dry-yield factor. Use builder's (soft) sand, not sharp sand, and use mortar within 2½ hours of mixing (2 hours in hot weather, BIA TN 8).
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Frequently asked questions
How much mortar do I need per square metre of brickwork?
The joints alone in a single-leaf wall of 215×65mm bricks with 10mm joints hold about 18 litres of mortar per square metre. Real use is higher — frogged bricks, buttering and droppings add to it — so allow extra. This calculator shows the joint volume plus your waste allowance, and allows extra headroom in the pre-mixed bag count.
What's the difference between Type M, S, N, and O mortar?
They are the four ASTM C270 mortar types, strongest to weakest. Typical cement:lime:sand mixes are Type M 1:¼:3¾, Type S 1:½:4½, Type N 1:1:6 and Type O 1:2:9, with lab-tested 28-day minimums of 2,500, 1,800, 750 and 350 psi. The Brick Industry Association recommends Type N for most above-grade brickwork, Type S for reinforced or loadbearing exterior walls, Type M for foundation and retaining walls, and Type O as an alternate for interior partitions and repointing.
How many 80 lb bags of pre-mixed mortar do I need?
Quikrete states that each 80 lb bag of its Mortar Mix will lay up to 37 standard bricks or 13 standard 8×8×16 in blocks. This calculator allows about 10.5 litres of joint volume per bag — roughly 35 UK-size bricks at 10 mm joints — so treat the bag count as an estimate and check the coverage printed on your product.
Should I use sharp sand or builder's sand for mortar?
Use builder's (soft) sand for brick and block mortar — it has rounder, finer particles that give a workable mix. Sharp sand is coarser and is meant for concrete and screeding, not mortar joints.