Concrete Slab Calculator

Minimum 4" (10cm) for walkways and patios. 5" for light vehicle traffic. 6" (15cm) for residential driveways and garage floors—this is the most common. 8"+ for heavy trucks, equipment, or commercial applications. Thicker slabs require less reinforcement but use more concrete. Always follow local building codes for specific requirements.

Calculate: Length × Width × Thickness (in feet) ÷ 27 = cubic yards. For a 20×20 ft slab at 4" thick: 20×20×(4/12)÷27 = 4.9 yd³. Add 10% for waste. Order full yards—ready-mix trucks deliver in 0.5 or 1 yard increments. This calculator handles all math automatically including waste factor.

Concrete costs: USA $4-8/sq ft installed ($120-180/yd³ materials); Canada C$6-12/sq ft; UK £50-100/m²; Australia A$60-150/m²; India ₹150-350/sq ft. Material is 30-40% of total—labor, site prep, and finishing are major costs. DIY can save 50%+ but requires skill and equipment for quality results.

Yes, 4-6" (10-15cm) of compacted gravel base is essential. It provides drainage, prevents soil movement, and creates uniform support. Use 3/4" crushed stone, compacted in 2" lifts. On expansive clay soils, thicker base (8"+) helps. Skip gravel only on well-drained sandy soils—and even then, 2-4" is recommended for best results.

Wire mesh (6×6 W1.4/W1.4) is standard for 4" residential slabs—controls cracking. Rebar (#4 @ 18" OC) is stronger for driveways and thicker slabs. Fiber reinforcement is another option for crack control. For garage floors and driveways, many contractors prefer rebar over mesh. Reinforcement should be in lower third of slab, supported on chairs.

Light foot traffic: 24-48 hours. Furniture and normal use: 7 days. Vehicle traffic: 7-14 days minimum, 28 days ideal. Full strength: 28 days. Keep concrete moist for first 7 days (curing) for best strength. Hot/dry weather requires longer curing. Cold weather slows curing—protect from freezing for at least 48 hours.