CalculatorMulchHow much potting soil will your containers take?
Potting soil calculator
58 dry quarts of mix
= 2.3 cu ft for 3 pot(s)
- 1.5 cu ft bags
- 2
- 1 cu ft bags
- 3
- In cubic yards
- 0.08
Diameter is measured across the rim, inside the lip โ not across the base.
What the yard needs this month
MonthlyOne job a month, with the depth and the volume it actually needs. No plant catalogues, no upsell โ just the material side of the garden.
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How much potting soil does a pot need?
A standard 14-inch round pot filled to an inch below the rim takes about 0.75 cubic feet of mix โ roughly 19 dry quarts โ so three of them need about 58 quarts, or two 1.5 cu ft bags. Potting mix is the one material sold in dry quarts rather than cubic feet, and 1 cubic foot is 25.7 dry quarts.
The reason you cannot just use the cylinder formula is that pots taper. A nursery pot measured across the rim holds noticeably less than a true cylinder of that diameter, so this calculator applies a 0.78 taper factor before subtracting the watering gap at the top. Skip that and you will overbuy by about a quarter.
Do not fill containers with garden soil or topsoil. Both compact in a pot until roots cannot breathe and water sits on the surface. Potting mix is a peat or coir and bark blend built to stay open โ which is also why it weighs around 700 lb a cubic yard, a third of what topsoil does.
Container gardening is where the arithmetic gets fiddly, because nothing shares a unit. Pots are sized in inches across the rim, mix is sold in dry quarts or cubic feet depending on the brand, and the pot itself holds less than its dimensions suggest.
The table below is the conversion for common round pots, filled to an inch below the rim with the taper allowed for. Heights are the usual proportion for each diameter.
| Pot (diameter ร height) | Cubic feet | Dry quarts |
|---|---|---|
| 8 ร 7 in | 0.14 | 3.7 |
| 10 ร 9 in | 0.29 | 7.4 |
| 12 ร 11 in | 0.51 | 13.0 |
| 14 ร 12 in | 0.75 | 19.3 |
| 16 ร 14 in | 1.14 | 29.4 |
| 20 ร 17 in | 2.17 | 55.8 |
A patio of a dozen mixed pots typically comes to four or five cubic feet โ three 1.5 cu ft bags, and no reason to look at bulk soil at all.
Frequently asked questions
How many quarts of potting soil are in a cubic foot?
25.7 dry quarts. A 1.5 cu ft bag is therefore about 38.6 dry quarts, and a 2 cu ft bag about 51.4. Watch the unit on the bag: US potting mix is labelled in dry quarts, which are 16 percent larger than the liquid quarts on a milk carton, and comparing the two is how people end up a bag short.
How much potting soil for a 12-inch pot?
About 0.5 cubic feet, or 13 dry quarts, filled to an inch below the rim. A 10-inch pot takes roughly 0.29 cubic feet (7.4 quarts) and a 16-inch pot about 1.14 cubic feet (29 quarts). One 1.5 cu ft bag fills just under three 12-inch pots, or two 14-inch ones.
How much soil does a window box or a rectangular planter need?
Length ร width ร depth in inches, divided by 1,728 to get cubic feet, then take 90 percent for the watering gap. A 36 ร 8 ร 7 in window box is 2,016 cubic inches โ 1.17 cubic feet brim full, 1.05 after the gap, or about 27 dry quarts. One 1.5 cu ft bag does it.
Can I reuse last year's potting mix?
Yes, for most ornamentals, if nothing in the pot was diseased. It will have compacted and lost structure, so refresh it: tip it out, break it up, and blend one part fresh mix or compost into three parts old. For seedlings and anything in the tomato and potato family, start with new mix.
Do I need gravel in the bottom of the pot?
No โ it is the most persistent myth in container growing. A coarse layer under fine mix raises the perched water table rather than lowering it, leaving the root zone wetter, not drier. Fill the pot with mix to the bottom and make sure the drainage hole is open.
How much does a filled container weigh?
Potting mix runs about 700 lb per cubic yard dry, so a 14-inch pot holding 0.75 cubic feet is roughly 19 lb dry and around 30 lb watered. A 24-inch planter at 3.7 cubic feet is 95 lb dry and closer to 150 lb wet โ worth knowing before you site one on a balcony or plan to move it.
How we calculate this
Worked example
With Pot diameter (inches) 14, Pot height (inches) 12, How many pots 3, Fill level 1 in below the rim (normal), this page works out 58 dry quarts of mix. = 2.3 cu ft for 3 pot(s)
- 1.5 cu ft bags2
- 1 cu ft bags3
- In cubic yards0.08
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