Potting soil calculator: how much potting soil do I need for my pots?
3 bags
of 8 qt · 20.2 dry quarts · 0.79 cu ft · 1,357 cu in · for a round pot 12 in across and 12 in deep
Run your own numbers
Enter it the way you measured it: 4.5, 4 1/2,
3/8 or 10' 6".
3 bags
of 8 qt · 20.2 dry quarts · 0.79 cu ft · 1,357 cu in
Source: AmericanHort, American Standard for Nursery Stock, ANSI Z60.2-2025, Table 1 Container class volume ranges, read October 21, 2026. Data sheet (PDF)
A round pot 12 inches across and 12 inches deep holds 1,357 cubic inches, 20.2 dry quarts, so it takes 3 bags of 8 qt: bagged soil is sold in dry quarts of 67.2 cubic inches (NIST Handbook 130), not liquid quarts.
A worked example
Seven square planters 10 1/2 inches wide with 9 inches of soil, filled from 1.5 cu ft bags needs 3 bags. Each planter holds 992 cubic inches, 6,946 for the seven: 4.02 cubic feet or 103.4 dry quarts, which is 2.68 bags of 1.5 cubic feet, so 3.
How much soil fills a 5 gallon pot?
Between 785 and 1,242 cubic inches if it is a #5 nursery pot: that is the ANSI Z60.2-2025 range for the class, 3.4 to 5.38 gallons, or 11.7 to 18.5 dry quarts. Three 8 qt bags fill the largest #5 pot and two the smallest. A 5 gallon bucket filled to the brim is 1,155 cubic inches, 17.2 dry quarts.
How many quarts of potting soil are in a cubic foot?
25.7 dry quarts, the quart bagged soil is sold in: NIST Handbook 130 makes it 1/32 of a 2,150.42 cubic inch bushel, 67.2 cubic inches. In liquid quarts of 57.75 cubic inches a cubic foot would be 29.9, which is why an 8 qt bag is 0.31 cubic feet and not 0.27.
Is a 1 gallon pot really 1 gallon?
Not always: a #1 nursery pot, sold as 1 gallon, may hold anywhere from 152 to 251 cubic inches by ANSI Z60.2-2025 Table 1, which is 0.66 to 1.09 gallons. The trade name is a class, not a volume, so measure the pot when the count matters.
What else it is called
Potting soil is also sold as potting mix or container mix, and searched as a potting soil calculator or how much potting soil for a 12 inch pot. Bags print their size in quarts or cubic feet; both are here, and the quarts are dry quarts.
Nursery pot sizes
| Pot class | Cubic inches | Gallons | Dry quarts | 8 qt bags to fill the largest |
|---|---|---|---|---|
| #1 | 152 to 251 | 0.66 to 1.09 | 2.3 to 3.7 | 1 |
| #2 | 320 to 474 | 1.39 to 2.05 | 4.8 to 7.1 | 1 |
| #3 | 628 to 742 | 2.72 to 3.21 | 9.3 to 11.0 | 2 |
| #5 | 785 to 1,242 | 3.40 to 5.38 | 11.7 to 18.5 | 3 |
| #7 | 1,337 to 1,790 | 5.79 to 7.75 | 19.9 to 26.6 | 4 |
| #10 | 2,080 to 2,646 | 9.00 to 11.45 | 31.0 to 39.4 | 5 |
| #15 | 2,768 to 3,696 | 11.98 to 16.00 | 41.2 to 55.0 | 7 |
| #20 | 4,520 to 5,152 | 19.57 to 22.30 | 67.3 to 76.7 | 10 |
| #25 | 5,775 to 6,861 | 25.00 to 29.70 | 85.9 to 102.1 | 13 |
Container class volume ranges from ANSI Z60.2-2025 Table 1, in cubic inches; gallons at 231 cubic inches, as the standard converts them; dry quarts of 67.2 cubic inches, the quart of NIST Handbook 130 that bagged soil is sold in. A #1 pot holds 0.66 to 1.09 gallons, not one gallon.
Where the numbers come from
- Nursery pot classes: American Standard for Nursery Stock, ANSI Z60.2-2025 (AmericanHort, approved April 17, 2025), Table 1: a #1 container holds 152 to 251 cubic inches, #2 320 to 474, #3 628 to 742, #5 785 to 1,242, #7 1,337 to 1,790, #10 2,080 to 2,646, #15 2,768 to 3,696, #20 4,520 to 5,152 and #25 5,775 to 6,861. Containers sold with a # designation must fall in these ranges, and section 1.1.3.4 converts gallons × 231 = cubic inches. Read October 21, 2026. Read the standard (PDF)
- Bag quarts: NIST Handbook 130-2026, Uniform Packaging and Labeling Regulation, sells dry measure by the U.S. bushel of 2,150.42 cubic inches and its dry quart subdivisions: 2,150.42 ÷ 32 = 67.2 cubic inches, or 1.101 liters. A liquid quart is 57.75. An 8 qt bag holds 537.6 cubic inches, and a cubic foot is 25.7 dry quarts. Read October 21, 2026. Read Handbook 130
- The rest is geometry: a round pot holds π × (diameter ÷ 2)² × depth and a square one width² × depth, in cubic inches; a nursery class is counted at the top of its range so the bags do not come up short.
A tapered pot holds less than a cylinder of its top width: measure the diameter halfway down for a closer count. This counts the soil that fills the pot, not the settling after the first watering, which no standard sets.
By Javier Miralles · Last updated . How this site is made.
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