Concrete Slab Calculator
Calculate the volume of concrete and number of cement bags needed for your slab.
Planning a concrete slab for a patio, garage floor, or foundation? Accurately estimating materials is essential to avoid costly over-ordering or project delays from shortages.
A concrete slab's volume is calculated by multiplying its length, width, and thickness. The result in cubic meters determines how much ready-mix concrete to order or how many bags of cement you need. A standard 50 kg bag of Portland cement yields approximately 0.159 m³ of concrete when mixed with sand and gravel — so roughly 6.3 bags are needed per cubic meter.
For most residential applications, a thickness of 100–150 mm (4–6 inches) is standard. Driveways and garage floors may require 150–200 mm. Always add 5–10% extra to account for uneven ground and spillage. Proper sub-base preparation and reinforcement with steel mesh or rebar will ensure your slab lasts for decades.