Reference
What does a bag of soil fill?
Bag sizes are printed in three different units depending on the brand. Here they are in one place, with the bag counts that follow.
Bag sizes compared
| Bag | Litres | Cubic feet | US dry quarts |
|---|---|---|---|
| 1 cu ft bag | 28.3 | 1.00 | 25.7 |
| 2 cu ft bag | 56.6 | 2.00 | 51.4 |
| 8 qt bag | 8.8 | 0.31 | 8.0 |
| 16 qt bag | 17.6 | 0.62 | 16.0 |
| 20 L bag | 20.0 | 0.71 | 18.2 |
| 40 L bag | 40.0 | 1.41 | 36.3 |
| 50 L bag | 50.0 | 1.77 | 45.4 |
| 60 L bag | 60.0 | 2.12 | 54.5 |
| 70 L bag | 70.0 | 2.47 | 63.6 |
Bags per raised bed
At 12 in deep with a 2 in drainage layer, rounded up. Add 10% to the bag count if you are also filling pots from the same order.
| Bed | 1 cu ft bag | 2 cu ft bag | 20 L bag | 40 L bag | 50 L bag | 60 L bag | 70 L bag |
|---|---|---|---|---|---|---|---|
| 4 × 4 ft | 15 | 8 | 22 | 11 | 9 | 8 | 7 |
| 4 × 8 ft | 30 | 15 | 43 | 22 | 17 | 15 | 13 |
| 4 × 12 ft | 45 | 23 | 64 | 32 | 26 | 22 | 19 |
| 3 × 6 ft | 17 | 9 | 24 | 12 | 10 | 8 | 7 |
| 2 × 8 ft | 15 | 8 | 22 | 11 | 9 | 8 | 7 |
| 5 × 10 ft | 47 | 24 | 67 | 34 | 27 | 23 | 19 |
Unit conversions
Bulk versus bags
Bagged soil is convenient and consistent; bulk is far cheaper per litre once you pass about a cubic yard. A cubic yard is 27 cubic feet, which fills a 4 × 8 ft bed to 10 in with some left over. Bulk delivery also means it arrives in a pile on your drive, which is worth thinking about before ordering.
If you are filling several beds, price it both ways. The break-even is usually somewhere around 700 to 900 litres, depending on local delivery charges.
Weight, before you carry it
Wet potting mix is roughly 0.45 to 0.5 kg per litre, so a 40 L bag weighs around 18 to 20 kg. Compost-heavy blends and topsoil mixes are heavier: up to 1.4 kg per litre. If the soil is going onto a balcony or a roof, the loaded weight matters more than the volume, and the calculator reports it.