Block Calculator

Standard 8×8×16 inch (200×200×400mm) CMU blocks cover 0.89 sq ft (0.08 m²) each including mortar joint. You need approximately 1.125 blocks per square foot or 12.5 blocks per square meter. A typical 8-foot (2.4m) high wall requires 9 courses of standard blocks. For a 100 linear foot (30m) foundation wall at 8 feet high, you need about 900 blocks. Add 5-10% for waste and breakage.

One 80-lb (36 kg) bag of mortar mix typically lays 12-15 standard concrete blocks. For 100 blocks, you need approximately 7-8 bags of mortar. Type S mortar is recommended for below-grade and load-bearing walls; Type N for above-grade non-structural walls. Mortar joint thickness is typically 3/8 inch (10mm). Factor in additional mortar for grouting hollow cores if reinforcing with rebar.

Block sizes vary by region: USA/Canada standard is 8×8×16 in (actual 7-5/8×7-5/8×15-5/8 in) with metric equivalent 200×200×400mm. UK uses 440×215×100mm as standard. Australia uses 390×190×190mm. European standard is 400×200×200mm. India uses 400×200×200mm or 390×190×190mm. Always verify local sizes as "standard" dimensions include mortar joints—actual blocks are slightly smaller.

Block prices vary: USA $1.25-3.00 per standard block; UK £1.50-3.00; EU €1.00-2.50; Australia A$3-6; India ₹30-50; South Africa R8-15; Malaysia RM2-4. Hollow blocks cost less than solid. Decorative split-face or colored blocks cost 2-3× more. Bulk orders (500+ blocks) often qualify for discounts. Delivery adds significant cost for small orders—plan efficiently.

Hollow blocks are standard for most walls—they're lighter (28-35 lb vs 40-50 lb), allow rebar insertion, and provide better insulation. Cores can be grouted for structural strength. Solid blocks are used for fire walls, pilasters, and where maximum strength is needed. For retaining walls and foundations, hollow blocks with grouted cores and rebar provide excellent strength at lower weight and cost than solid blocks.

Reinforcement requirements depend on location, height, and purpose. Most building codes require vertical rebar at corners, door/window openings, and every 4-8 feet (1.2-2.4m). Horizontal reinforcement (ladder wire or bond beam blocks with rebar) typically every 2-4 courses. Retaining walls always need reinforcement. Consult local building codes—seismic zones require significantly more reinforcement. Fill reinforced cores with grout.