Work out how much concrete to order for a slab, path, driveway, strip footing, pad footing, pier or column. Enter each element in metres or millimetres as labelled. The calculator adds a wastage allowance, rounds up to the next 0.2 m³ (the usual premix order increment in Perth), tells you how many truck loads to expect and warns you if the last load will attract a short-load fee.
Concrete calculator (metric)
Add each slab, footing, column or pier as its own row. Enter sizes in metres or millimetres as labelled. The calculator adds your wastage allowance and rounds the order up to the next 0.2 m³.
Supply settings
Volumes are theoretical. Wastage covers over-dig, uneven subgrade, spillage and pump line losses. Truck capacity and short-load limits vary between Perth suppliers, so check before you order. Concrete grade, thickness and reinforcement must follow your engineer's drawings and AS 2870 / AS 3600. Bag count assumes 108 × 20 kg premix bags per m³.
Need the whole slab, footings and reinforcement measured from your plans?
Measure Manage prepares professional concrete take-offs and estimates for Perth and WA builders, from house slabs to civil works: volumes by element, mesh and bar reinforcement, formwork and a priced summary. Call Alastair on 0498 202 445 for a professional take-off.
How the concrete calculator works
- Slabs, paths and driveways: length × width × thickness.
- Strip and pad footings: length × width × depth.
- Round columns and bored piers: π × (diameter ÷ 2)² × height × quantity.
- Square columns: width × width × height × quantity.
Wastage is added to each element, because footings in sand and bored piers usually need more allowance than a formed slab. The total is then rounded up to the order increment you set.
How much wastage should I allow?
- Formed slabs and paths: about 5%.
- Trench footings and piers in sand: about 10%, more if the trench sides collapse.
- Pumped pours: allow for the line volume and priming.
Ordering premix concrete in Perth
- Order in 0.2 m³ increments and confirm the grade (for example N20, N25 or N32) your engineer has specified.
- Small loads often carry short-load or minimum-cartage fees, so check with your supplier. The calculator flags any final load under the threshold you enter.
- Book a pump for anything you can’t reach with the truck chute or a barrow.
- Hot Perth summers shorten working time, so plan early-morning pours.
What this calculator doesn’t include
- Reinforcement, mesh, bar chairs and joints
- Formwork, sand bed and vapour barrier
- Labour, pumping and finishing
- Excavation and spoil removal
Frequently asked questions
How do I calculate how much concrete I need?
Multiply length × width × depth in metres to get cubic metres, then add wastage. For example, a 6 m × 4 m slab 100 mm thick is 6 × 4 × 0.1 = 2.4 m³. With 5% wastage that’s 2.52 m³, so order 2.6 m³.
How many 20 kg bags of concrete make a cubic metre?
Roughly 108 bags of 20 kg premix per m³, depending on the product. Check the yield on the bag. For anything over about half a cubic metre, ready-mix is usually cheaper and quicker.
How do I estimate the cost?
Enter your supplier’s price per m³ to get a materials cost. Then add delivery fees, pumping, reinforcement, formwork and labour for a full price.
Need the whole job measured? Measure Manage prepares material take-offs and construction estimates for Perth and WA builders. Call 0498 202 445.