FIELD GUIDE
How many bags of concrete do you need?
A bag count starts with the space you need to fill. Multiply the dimensions to get volume, add an allowance for uneven ground and spillage, then divide by the mixed volume one bag produces. Round up to a whole bag.
Typical bag yields
For standard QUIKRETE Concrete Mix, the published approximate yields are:
| Bag size | Mixed yield | Approximate litres |
|---|---|---|
| 60 lb (27.2 kg) | 0.45 ft³ | 12.7 L |
| 80 lb (36.3 kg) | 0.60 ft³ | 17 L |
These are product assumptions, not a rule for every bag. Read the label of the mix you plan to buy. Some specialty mixes produce a different volume. Source: QUIKRETE Concrete Mix technical data.
Worked example: a 10 × 10 ft slab
A 10 ft by 10 ft slab that is 4 in thick has 33.33 ft³ of space to fill. With 10% waste, plan for 36.67 ft³. At 0.60 ft³ per 80 lb bag, that is 61.12 bags, so buy at least 62 bags. At 0.45 ft³ per 60 lb bag, it is 81.49 bags, so buy at least 82 bags.
The same slab needs 1.36 yd³ after the allowance when rounded up to hundredths. If ordering ready-mix, ask the supplier about minimum loads and ordering increments.
Why the answer can change
- Actual excavated depth can vary across the site.
- Form dimensions may differ from the planned measurements.
- Waste varies with placement method and site conditions.
- The bag's stated mixed yield may differ from this guide.
Re-measure before ordering. For structural work, follow your plans, local code, and the advice of a qualified professional. The calculator estimates quantity; it does not design a structure.