Mortar Calculator

One 80-lb (36 kg) bag of mortar mix lays approximately 30-40 standard bricks or 12-15 concrete blocks. Coverage depends on joint thickness—3/8" (10mm) joints use less than 1/2" (12mm). For 1000 bricks, plan for 25-30 bags. For 100 blocks, need 7-8 bags. Experience matters—beginners use more due to waste and rework.

Type N is standard for above-grade walls, chimneys, and general use—good balance of strength and workability. Type S is stronger for below-grade, load-bearing walls, and foundations. Type M is highest strength for heavy loads and below-grade. Type O is weak, for interior non-load-bearing only. Match mortar type to building code requirements.

Mortar bag prices: USA $6-12 per 80 lb bag; UK £5-10 per 25 kg; EU €4-9 per 25 kg; Australia A$10-20 per 20 kg; India ₹200-400 per 40 kg. Pre-mixed mortar costs more than site-mixing portland cement, lime, and sand, but saves labor and ensures consistency. Buy in bulk for large projects.

Mixed mortar should be used within 2-2.5 hours before it begins to set. In hot weather, this time shortens. Never add water to "re-temper" mortar that's started setting—it weakens the bond. Mix only what you can use in 90 minutes. Keep mortar covered and in shade while working. Discard any mortar that becomes stiff or crumbly.

Proper mortar should hold its shape when troweled but be workable enough to spread easily. It should stick to the trowel when held vertically without dripping. Too wet: sags and stains masonry. Too dry: doesn't bond properly and is hard to work. Add water gradually until reaching "butter-like" consistency that slides off the trowel cleanly.

Standard mortar joints are 3/8" (10mm) for brick and 3/8"-1/2" (10-12mm) for block. Consistent joint thickness is essential for appearance and structural integrity. Thicker joints require more mortar and are weaker. Use spacers or story poles to maintain consistent courses. Tool joints when "thumbprint hard" for weather resistance and appearance.