How much potting soil for a 5 gallon bucket or grow bag?
A 5 gallon bucket or grow bag filled to the top takes about 17 dry quarts of potting mix (0.67 cubic feet). With 10% for settling, plan on 19 dry quarts (0.74 cubic feet): a little more than one 16 qt bag, or about three-quarters of a 1 cu ft bag.
How to work it out
- 5 gal per container
- + 10% for settling = 0.74 cu ft (19 dry quarts) → 2 bags
Five-gallon buckets and grow bags are the standard size for a single tomato, pepper or potato plant. That is not an accident: University of Maryland Extension lists 5 gallons as the minimum for standard tomatoes, peppers, cucumbers and eggplant.
Adjust for your project
More options: Settling · Bag price
- In dry quarts (as on the bag)
- 19 dry quarts
- Bags of that size
- 2 bags · 16 qt bag
- Each container holds
- 5 gal (18.9 L)
- Pot and grow-bag sizes are often nominal — a "5-gallon" nursery pot usually holds noticeably less than 5 US gallons. Measure if it matters.
- Use potting mix, not garden soil or topsoil — soil packs down in a container and drains poorly.
Potting mix by container size
| Container | Potting mix to buy | In dry quarts (as on the bag) | Bags of that size |
|---|---|---|---|
| 1 gal | 0.15 cu ft | 4 dry quarts | 1 bag |
| 2 gal | 0.29 cu ft | 8 dry quarts | 1 bag |
| 3 gal | 0.44 cu ft | 11 dry quarts | 1 bag |
| 5 gal | 0.74 cu ft | 19 dry quarts | 2 bags |
| 7 gal | 1.03 cu ft | 26 dry quarts | 2 bags |
| 10 gal | 1.47 cu ft | 38 dry quarts | 3 bags |
| 15 gal | 2.21 cu ft | 57 dry quarts | 4 bags |
What to know about filling a 5 gallon container
Check how big it really is. Nursery pots sold as "#5" or "5 gallon", and many fabric grow bags, hold noticeably less than 5 US gallons. The easy test is to fill it with water from a gallon jug before you buy mix. A hardware-store bucket is usually close to its stated 5 gallons, but you fill it an inch or two below the rim, which takes off a quart or two.
A 16 qt bag nearly fills one, and one 1 cu ft bag fills one with about 7 quarts left over for top-ups. If you are planting a row of these, 2 cu ft bags are the better buy: each one fills two containers and a bit.
Drill drainage holes in a bucket. University of Maryland Extension says every container needs holes in the bottom, and a plain bucket has none; several holes around the base, not one in the middle, drain it evenly.
Don’t fill it with garden soil to save money. Maryland puts garden soil at about 75 lb per cubic foot against roughly 10 lb for a soilless mix, so a bucket of soil weighs something like 50 lb before watering and packs down hard.
For a smaller pot, see How much potting soil for a 12 inch pot; for a large planter, How much soil for a half whiskey barrel planter.
Different size? Use the full Potting Soil Calculator.
What you’ll need
- Potting soil scoopBudget price
Fills pots from a bag with less mess than a trowel.
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Easier than a wheelbarrow for hauling bags and pots, and it tips to unload. Check the rated load against what you will carry.
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Frequently asked questions
How much potting soil for a 7 gallon grow bag?
About 24 dry quarts (0.94 cubic feet) if it holds a full 7 gallons; 26 dry quarts with 10% for settling.
How much potting soil for a 10 gallon grow bag?
About 34 dry quarts (1.34 cubic feet); 38 dry quarts with 10% for settling, which is 3 bags of 16 qt or one 1.5 cu ft bag.
How many 2 cu ft bags of potting mix for four 5 gallon buckets?
2 bags of 2 cu ft for 76 dry quarts (2.94 cubic feet), including 10% for settling.
Other common sizes
- How much potting soil for a 12 inch pot — 0.48 cu ft
- How much soil for a half whiskey barrel planter — 4.57 cu ft
Sources
- University of Maryland Extension: Growing Vegetables in Containers and Salad Tables (opens in a new tab) — Garden soil (~75 lb/cu ft) is too dense for containers; soilless mixes are ~10 lb/cu ft; minimum container sizes (5 gal for standard tomatoes, peppers, cucumbers, eggplant; 2 gal for cherry tomatoes).
- University of Maryland Extension: Types of Containers for Growing Vegetables (opens in a new tab) — All containers need drainage holes; half whiskey barrels and 5-gallon buckets as containers; growing-media volume and depth by plant size.
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement (opens in a new tab) — 1 dry quart = 67.2006 cubic inches; 1 cubic foot = 1,728 cubic inches.