You need
- 2.62cu ft
- 74.1liters
- $29–$55for the bags
Prices: what garden centers post, October 2026.
- You need 67.3 quarts of potting mix to fill 4 pots.
- That is 2.62 cu ft. Or 74.1 liters.
- Buy 3 bags of 1 cu ft. They cost about $29 to $55.
- Most pots are smaller at the bottom. They hold a little less than this.
How much soil a pot holds
Round pots with straight sides, as deep as they are wide, filled to the top. Pots that get smaller at the bottom hold less.
| Pot | Quarts | Liters | Gallons |
|---|---|---|---|
| 6 in15 cm | 2.5 | 2.8 | 0.6 |
| 8 in20 cm | 6 | 6.6 | 1.5 |
| 10 in25 cm | 11.7 | 12.9 | 2.9 |
| 12 in30 cm | 20.2 | 22.2 | 5 |
| 14 in36 cm | 32.1 | 35.3 | 8 |
| 16 in41 cm | 47.9 | 52.7 | 12 |
| 20 in51 cm | 93.5 | 103 | 23.4 |
| 24 in61 cm | 161.6 | 177.9 | 40.4 |
This is our math. Garden guides do not agree on a 12 in pot. Ohio State says 3½ gallons. UVM says 7 to 9 quarts. So we work from the size of your pot.
Nursery pot sizes
A #1 pot is often called a 1 gallon pot. It is not always 1 gallon. The nursery rules give each size a range.
| Size | Holds | Quarts |
|---|---|---|
| #1 | 152 to 251 cu in2.5 to 4.1 L | 2.3 to 3.7 |
| #2 | 320 to 474 cu in5.2 to 7.8 L | 4.8 to 7.1 |
| #3 | 628 to 742 cu in10.3 to 12.2 L | 9.3 to 11 |
| #5 | 785 to 1,242 cu in12.9 to 20.4 L | 11.7 to 18.5 |
| #7 | 1,337 to 1,790 cu in21.9 to 29.3 L | 19.9 to 26.6 |
| #10 | 2,080 to 2,646 cu in34.1 to 43.4 L | 31 to 39.4 |
| #15 | 2,768 to 3,696 cu in45.4 to 60.6 L | 41.2 to 55 |
| #20 | 4,520 to 5,152 cu in74.1 to 84.4 L | 67.3 to 76.7 |
AmericanHort, ANSI Z60.2-2025, Table 1.
Bag sizes and quarts
Bags are sold in quarts or cubic feet. One cubic foot is about 25.7 quarts. So an 8 qt bag is about 0.3 cu ft. A 2 cu ft bag holds about 51 quarts.
Small bags cost more for the same mix. Garden centers post about $19.25 to $35.33 a cubic foot for bags under 1 cu ft. Big bags are about $9.74 to $18.49.
Filling a raised bed? Use the raised bed soil calculator. It is cheaper in bulk.
How the math works
- Round pot. Half the width times itself, times 3.1416, times the soil depth. That gives cubic inches. We treat the sides as straight.
- Box. Length times width times the soil depth.
- Nursery pot. The low and high of its size, from the nursery rules.
- Units. 1,728 cubic inches make 1 cu ft. One cu ft is 25.714 dry quarts and 28.3 liters. We read the quarts on a bag as dry quarts.
- Bags. Cubic feet divided by the bag size, rounded up.
- Price. What garden centers post, by bag size, in October 2026. We leave out the cheapest and dearest tenth.
Questions
How much potting soil do I need for a pot?
A 12 in round pot, 10 in deep, holds about 17 quarts. That is about 0.65 cu ft. Type your pot above to get yours.
How many quarts are in a cubic foot?
About 25.7 dry quarts. So a 1 cu ft bag holds about 26 quarts.
How much soil does a 5 gallon pot hold?
A #5 nursery pot holds 785 to 1,242 cubic inches. That is about 12 to 18.5 quarts. It is often less than 5 gallons.
How big a pot does a tomato need?
NC State says a 5 gallon pot for one tomato plant. Peppers need 2 gallons. Lettuce needs 2 quarts.
Is it cheaper to buy big bags?
Yes. Small bags cost about twice as much for each cubic foot.
Sources
- AmericanHort, American Standard for Nursery Stock, ANSI Z60.2-2025Apr 2025What each nursery pot size holds
- Ohio State HYG-1647, Container Vegetable Gardening2000Soil for each pot size, a check
- UVM Extension, Gardening in Small Spaces on a BudgetApr 2023A 12 in pot holds 7 to 9 quarts, a check
- NC State Extension Gardener Handbook, Ch. 18undatedPot size for each vegetable
- NIST Handbook 130 (2026)2026The dry quart: 1 cu ft is 25.7 dry quarts