Formula
Order volume = Net volume × (1 + wastage % ÷ 100), rounded up to the ordering step
Truck loads = ⌈ Order volume ÷ Truck capacity ⌉
Last load = Order volume − (Truck loads − 1) × Truck capacity⌈ ⌉ means “round up to the next whole number”. You cannot order a fraction of a truck.
Worked Example
A ground slab 20 m long, 12 m wide and 200 mm thick, poured with 8 m³ trucks:
- Net volume = 20 × 12 × 0.20 = 48.0 m³
- With 5% wastage = 48.0 × 1.05 = 50.4 m³
- Round up to the next 0.5 m³ = 50.5 m³ to order
- Trucks = ⌈50.5 ÷ 8⌉ = ⌈6.31⌉ = 7 trucks
- Six full trucks carry 48 m³; the seventh carries 2.5 m³
That last load is under a third of the drum. Before you place the order, ask the plant whether a short-load charge applies, or whether two 9 m³ trucks at the end would work better.
Trucks Needed by Pour Volume
Order volume already includes wastage. Each figure is rounded up.
| Order volume | 6 m³ trucks | 8 m³ trucks | 10 m³ trucks |
|---|---|---|---|
| 10 m³ | 2 | 2 | 1 |
| 20 m³ | 4 | 3 | 2 |
| 30 m³ | 5 | 4 | 3 |
| 50 m³ | 9 | 7 | 5 |
| 100 m³ | 17 | 13 | 10 |
Planning the Pour on Site
- Spacing the trucks. Divide your placing rate (pump or crane output, often 20–40 m³/h on a slab) by the truck size to get the arrival interval. At 30 m³/h and 8 m³ trucks, you need a truck about every 16 minutes.
- Hold the last truck. Ask the plant to batch the final truck only after you call it in, once you can measure the actual remaining volume.
- Check the volume against the drawings. Slab thickness on site is often more than drawn because of subgrade levels. A 10 mm overrun on a 240 m² slab is another 2.4 m³: a third of a truck.
Assumptions
- The calculator works with whatever truck capacity you enter. Defaults are 8 m³ (metric) and 10 yd³ (imperial).
- Orders are rounded up to 0.5 m³ or 0.25 yd³.
- Volume is for a rectangular pour. For footings, columns and beams, use the concrete volume calculator and enter the total here with “Total volume”.