Pot Size Conversion Chart
How much soil do I need for my container?
Today was one of those days I wish there were something "standardized" about pot sizes. One catalog uses one set of measurements; another catalog uses something else. Stores use inches; nurseries use gallons. Ahhhh...
To add to the confusion, in the U.S., most nursery and garden centers use and sell pots by the inch or gallon, but in most of Europe, pot containers are sold by metric units, in centimeters or liters.
Trying to figure out pot sizes is often quite a headache. You've got some in inches, some in gallons, and yes, even some in fluid ounces; the latter we're still trying to figure out. They do make this confusing, don't they? There's a theory going around that this purposely confusing system is a way for the mass market industry to charge more for plants, by the container size, not necessarily Plant Size!
While the volume of any given pot can vary based on its depth, width, and whether it is tapered or not, we've attempted to provide a rough guide below. Additionally, to determine the size of a pot, you'll typically measure across the top to determine the size (inches or centimeters).
So let's try and break down these various sizes and measurements and set some general "accepted standards" for pot sizes. Please remember these are rough estimates and not a science. Some of the larger sizes especially are prone to variances in height, width, and depth of the pot. We've also attached a photograph that we hope will help allow you to visualize the differences.
Pot Size Conversion Chart
Inches to Gallons to Liters to Cubic Feet
| Pot Sizes (inches) | Pot Equivalent (U.S. Gallons) | Dry Soil Needed (Approx. cu.ft.) |
| 4" pot | pint / 0.5 quart / .125 gallon | 0.01 ft3 |
| 5-6" pot | quart / 0.25 gallon | 0.03 ft3 |
| 7-8" pot | 1 gallon | 0.13 ft3 |
| 8.5" pot | 2 gallon | 0.26 ft3 |
| 10" pot | 3 gallon | 0.40 ft3 |
| 11" pot | 4 gallon | 0.53 ft3 |
| 12" pot | 5 gallon | 0.66 ft3 |
| 13" pot | 6 gallon | 0.80 ft3 |
| 14" pot | 7 gallon | 0.94 ft3 |
| 16" pot | 10 gallon | 1.33 ft3 |
| 18" pot | 15 gallon | 2.00 ft3 |
| 21" pot | 20 gallon | 2.67 ft3 |
| 24" pot | 25 gallon | 3.34 ft3 |
| 30" pot | 30 gallon | 4.01 ft3 |
| Pot Sizes (inches) | International (Liters) | |
| 4" pot | .5 L [.473] | |
| 5-6" pot | 1 L [.946] | |
| 7-8" pot | 4L [3.78] | |
| 8.5" pot | 7.5 L [7.57] | |
| 10" pot | 11 L [11.35] | |
| 11" pot | 15 L [15.14] | |
| 12" pot | 19 L [18.92] | |
| 13" pot | 22.5 L [22.71] | |
| 14" pot | 26.5 L [26.49] | |
| 16" pot | 38 L [37.85] | |
| 18" pot | 57 L [56.78] | |
| 21" pot | 75.5 L [75.70] | |
| 24" pot | 94.5 L [94.63] | |
| 30" pot | 113.5 L [113.56] |
Download Pot Sizes Conversion Chart
Download the conversion chart in PDF format.
Frequently Asked Questions
Are nursery pot sizes actually standardized?
No. "Gallon" sizes in the nursery trade are trade gallons, not actual U.S. liquid gallons. A "1-gallon" nursery pot typically holds about 0.7 actual gallons. The industry has never standardized this, which is why measurements vary between manufacturers and retailers.
Should I measure my pot from the inside or outside?
Measure across the top, inside rim to inside rim. That gives you the diameter most catalogs and retailers reference. Outside measurements include the pot wall thickness and will read slightly larger.
How much soil do I actually need to fill a container?
Use the cubic feet column in the chart above as a starting point, but expect to use 10-15% less than listed. Most gardeners leave an inch or two of space below the rim for watering, and tapered pots hold less volume than straight-sided ones at the same diameter.
Does pot shape affect how much soil I need?
Yes. A tall, narrow pot and a short, wide pot with the same diameter hold very different volumes. The chart assumes standard nursery proportions. Bowl-shaped or tall columnar pots will need more or less soil than listed. When in doubt, measure the actual volume with water first.
