How do I calculate concrete for a column or pier?
Volume = π × (diameter ÷ 2)² × height, all in metres. A 450 mm diameter pier 1.2 m deep is about 0.19 m³ before wastage.
Concrete column and pier calculator
SLABSET
VOLUME0.00m³includes 10% wastage
TO ORDER0 Bags (20kg) or 0.0 m3 Premix
To order
0.00m³
Inputs
ShapeColumn
Diameter0 mm
Height0 mm
Wastage+10%
Estimated cost
Recommended: –Enter dimensions to estimate cost.
Individual bags–
0 × 20 kg · 0 × 30 kg
Ready-mix delivery–
0.0 m³ + delivery (ex pump)
Typical metro prices in Australia. Confirm with your local supplier before ordering.
Materials & weight
Reinforcing mesh0 sheets
Formwork edge0.0 m
Concrete weight0.00 t
How it's calculated
Concrete is sold by volume in m³. Measure the space, work out its volume, add wastage, then convert to individual bags or a premix order.
Wastage: sites lose concrete to spillage and uneven ground. 10% is standard; raise it for rough ground, lower it for tidy formwork.
Bags or premix: a 20 kg bag yields ≈ 0.0098 m³ (~102 bags/m³). Premix sells in 0.1 m³ steps; below 0.5 m³ bags usually avoid short-load fees.
About
Round columns, bored piers and post holes are cylinders: π × radius² × height. Enter the diameter and height in millimetres: a 450 mm auger hole at 1200 mm deep is about 0.19 m³ each.
For multiple identical piers, calculate one and multiply, or sum the total height. Post holes suit bags; a pier cage pour usually suits premix once you pass roughly 0.5 m³ total.
FAQ
How much wastage should I add?
10% is a normal starting point. Use less for tidy formwork and more for rough ground, uneven excavation or over-dig.
Should I order bags or premix?
Ready-mix is cheaper per cubic metre, but delivery and short-load fees make small deliveries poor value: suppliers charge extra below about 0.5 m³. Bags cost more per m³ but scale down to any size. The switchover is roughly 0.5 m³: below it, order bags; above it, book the truck.
Does this replace a builder or engineer?
No. Use SlabSet for estimating, then confirm quantities, grade and reinforcement before ordering.
Other calculators
Estimates only. Confirm quantities and prices with your supplier.
SlabSet · Metric Concrete Calculator · designed in Australia · Terms · Privacy · Contact