Calculate the volume of concrete needed for a slab, footing, or pad. Enter dimensions, choose a depth preset, and get volume, cost, and bag count instantly.
Calculate concrete volume from length × width × depth, with slab depth presets
Covers spillage, uneven sub-base, and over-dig
Measure the length and width of the area to be concreted. For depth, use 100mm for patios and sheds, 150mm for driveways, and 225mm or more for footings. Always check local building codes for minimum depth requirements.
Add 5-10% extra concrete to account for spillage, uneven sub-base, and over-excavation. For irregular shapes or sloping ground, use 10-15%. Ordering slightly more is always better than running short mid-pour.
For slabs over 2m³, ready-mix delivery is usually cheaper and faster. For smaller jobs (under 1m³), bagged concrete mixed on-site is more practical. A standard 25kg bag yields about 0.0125m³ of concrete.
Concrete reaches about 60% of its 28-day strength after 7 days. Keep it moist for at least 7 days (cure) to achieve full strength. Do not load heavily until at least 7 days have passed.
V = length × width × depth
V_total = V × (1 + waste%)
bags = ceil(V_total / yield_per_bag)
cost = V_total × price_per_m³
For structural concrete (foundations, retaining walls, suspended slabs), consult a structural engineer for mix design, reinforcement specification, and loading calculations. Building control approval may be required for concrete work in the UK.
Volume = 4 × 3 × 0.1 = 1.2 m³. With 5% waste: 1.26 m³. At £120/m³ ready-mix: about £151. You would need about 101 bags of 25kg concrete.
Patios and shed bases: 100mm. Driveways and car parks: 150mm. House footings: 225mm minimum (consult building control). Heavy-duty industrial: 200-300mm. Always check local building regulations.
Approximately 80 bags of 25kg concrete make 1m³ at standard mix ratio. Each bag yields about 0.0125m³. For a 1m³ slab, order at least 84 bags to account for 5% waste.
Multiply the volume in m³ by the price per m³ of ready-mix concrete. Typical UK ready-mix prices range from £100-150/m³ depending on mix design and delivery distance.