Calculate how much concrete you need for slabs, columns, and footings. Shows cubic meters, cubic yards, and the number of 25 kg or 40 kg bags. Free and instant.
0.9 m³
Volume (m³)
1.18 yd³
Volume (yd³)
87
25 kg Bags
44
50 kg Bags
71
60 lb Bags
53
80 lb Bags
Concrete
Calculating the required amount of concrete is critical for any construction project. Too little stops the job; too much is costly waste. The volume is calculated on a simple principle: for slabs and footings, it is length × width × thickness (in meters), and for a circular column, it is π × (diameter/2)² × height.
Our calculator supports both metric (cm/m³) and imperial (ft/in/yd³) systems, and automatically shows the number of bags of concrete in various sizes (25 kg, 50 kg, 60 lb, 80 lb).
Structure Types
Concrete slab — a horizontal structure: garage floors, patios, floor surfaces. Thickness is typically 10–20 cm for residential use. For heavier loads, it is reinforced with a metal mesh or rebar.
Circular column — a vertical element with a round cross-section: support pillars, fence posts. Diameter and height determine the volume using the cylinder formula. Square footing — a foundation under walls or columns: a rectangular volume with greater thickness.
Concrete Bags
For small projects, buying pre-mixed bags of concrete is more economical than ordering a truck. A 25 kg bag covers approximately 0.0104 m³, and a 50 kg bag covers about 0.0208 m³. In the American system, a 60 lb bag yields about 0.45 cubic feet (0.01274 m³), and an 80 lb bag yields about 0.60 cu ft (0.01699 m³).
For projects over 2–3 m³, ordering ready-mixed concrete by truck is more cost-effective. Always order with a 10% buffer for mixing and pouring losses.
Tips
Add a 10% buffer
Always order 5–10% more than calculated to account for mixing losses and surface irregularities.
Concrete grade
For foundations and slabs, use at minimum class C20/25. For driveways and garages, use C25/30 or higher.
Temperature matters
Do not pour concrete below 5°C or above 35°C without special measures — it will not cure properly.
Reinforcement
For slabs wider than 2 m and load-bearing structures, always reinforce with metal mesh or rebar.
Curing time
Concrete reaches 70% strength in 7 days and full strength in 28 days. Keep it moist during this period.
Ready-mix vs site-mixed
For volumes over 1 m³, ready-mix delivery is more consistent and saves significant time.
For a concrete slab, multiply length × width × thickness (all in the same unit). For example, a 3m × 3m slab at 10 cm (0.10 m) depth = 0.9 m³. Our calculator handles unit conversion automatically — enter dimensions in cm or ft/inches.
A standard 25 kg bag of concrete mix covers approximately 0.0104 m³, meaning you need about 96 bags per cubic meter. A 50 kg bag covers about 0.0208 m³ (48 bags/m³). For projects over 2 m³, ordering ready-mix concrete by truck is usually more economical.
A circular column uses the cylinder formula: π × (diameter ÷ 2)² × height. For example, a column with a 30 cm (0.3 m) diameter and 3 m height = π × 0.15² × 3 ≈ 0.212 m³.
Yes — it's recommended to add 5–10% to account for spillage, uneven surfaces, and mixing losses. If the slab area has irregular edges or the ground is not perfectly level, add 10% to be safe.
A slab is a horizontal surface (floor, patio, driveway), typically 10–20 cm thick. A footing is a structural foundation element placed under walls or columns, usually thicker (20–60 cm) and narrower, designed to transfer loads to the soil.