Bags per cubic metre
| Bag size | Per 1 m³ | Per 0.75 m³ | Per 0.5 m³ | Per 0.25 m³ | Typical products |
|---|---|---|---|---|---|
| 25 L | 40 | 30 | 20 | 10 | Potting mix, garden soil, manure |
| 30 L | 34 | 25 | 17 | 9 | Garden soil, compost, soil conditioner |
| 40 L | 25 | 19 | 13 | 7 | Premium garden and veggie mixes |
| 50 L | 20 | 15 | 10 | 5 | Potting mix, mulch |
| 60 L | 17 | 13 | 9 | 5 | Bark, wood-chip and sugar cane mulch |
| 70 L | 15 | 11 | 8 | 4 | Bark chips, pine bark |
All counts are rounded up to whole bags. If you want the exact figure or a different volume, the cubic metres to bags converter does it live.
The maths
A cubic metre is a cube one metre on each side. A litre is a cube ten centimetres on each side, and 10 × 10 × 10 of them fit inside a metre cube – hence 1,000. Bag sizes are printed in litres because that is how packing lines measure, so the conversion is pure division. The only judgement call is rounding: 33.3 bags of 30 L means you buy 34.
How much does a cubic metre weigh?
Volume is fixed; weight depends on the product and how wet it is. This matters for two reasons: what your car or trailer can carry, and how many trips 34 bags really is.
| Product | Weight per m³ (bulk) | Weight of a 30 L bag | Safe load, 6×4 trailer |
|---|---|---|---|
| Garden soil / veggie mix (moist) | 1,200–1,400 kg | 20–25 kg | ≈ 0.38 m³ bulk, or 20–25 bags |
| Compost | 500–700 kg | 15–20 kg | tray full, ≈ 0.65 m³ |
| Potting mix | 350–450 kg | 10–13 kg | tray full (space-limited) |
| Bark / wood-chip mulch | 250–450 kg | 8–13 kg | tray full (space-limited) |
| Sand | 1,400–1,600 kg | n/a (sold by weight) | ≈ 0.33 m³ |
| Gravel / crushed rock | 1,500–1,700 kg | n/a (20 kg bags) | ≈ 0.31 m³ |
Bagged garden soils are lighter than bulk soil of the same name, because they contain more compost and composted bark. That is why a 30 L bag weighs less than 30 L of bulk soil would, and why 20–25 bags weigh about the same as 0.38 m³ of bulk soil.
A standard 6×4 box trailer has a total rating (ATM) of 750 kg, and that includes the trailer's own 200–275 kg. That leaves roughly 500 kg of payload: only about 0.38 m³ of soil or a third of a cubic metre of gravel. A cubic metre of soil in a 6×4 trailer is illegal and unsafe. Mulch and compost are light enough that space, not weight, is the limit. The trailer load calculator works it out for your own trailer and car.
Why 34 bags may not fill a "cubic metre" bed
A raised bed measuring exactly 1 m³ inside will usually take more than 34 bags of 30 L, for two reasons. Bagged mix has been compressed in the bag and fluffs up when tipped, then settles again by 10–15 % once watered. And you will always lose a little to spillage and to the corners. Plan on 10–15 % extra for fresh mixes – the calculators on this site have a checkbox for it – and keep a couple of bags for topping up after the first month.
Questions
How many 25 L bags make a cubic metre?
Exactly 40. A 25 L bag of moist garden soil weighs about 18–22 kg, so a cubic metre is roughly 800 kg of bags.
How many litres in a cubic metre?
1,000 litres. A cubic metre is 1 m × 1 m × 1 m; a litre is 0.1 m × 0.1 m × 0.1 m.
How many bags of mulch in a cubic metre?
Mulch is usually sold in 50 L, 60 L or 70 L bags: 20, 17 or 15 bags per cubic metre. Bulk mulch is nearly always cheaper above about 0.6 m³.
Sources
- SI definition: 1 m³ = 1,000 L. All table values are exact division rounded up.
- Product weights from manufacturer listings and landscape-supply density tables (soil 1.2–1.4 t/m³, compost 0.5–0.7 t/m³, bark mulch 0.25–0.45 t/m³).
- Trailer payload from typical 6×4 box-trailer specifications (750 kg ATM, 200–275 kg tare) – see the trailer load calculator for the method.
Last reviewed 23 September 2026 · Report an error