Pot Size Guide
🌱 Pot Size Guide: Inches to Gallons Conversion
At 305 Greenery, we list pot sizes by their diameter in inches. Because many gardeners are more familiar with gallons, this guide shows you the approximate conversion between U.S. Gallons and Trade Gallons (the horticultural standard, ≈ 0.71 U.S. gal). This way, you’ll always know what to expect when choosing the right pot for your plant.
Why Trade Gallons vs. U.S. Gallons?
A Trade Gallon is slightly smaller than a true U.S. gallon. Growers use trade gallons to standardize pot sizes, while customers often think in U.S. gallons. Showing both helps eliminate confusion when you shop for plants.
| Pot Diameter (inches) | Approx. U.S. Gallons | Approx. Trade Gallons |
|---|---|---|
| 4" | ~0.25 | ~0.18 |
| 6" | ~1.0 | ~0.7 (≈ #1) |
| 8" | ~2.0 | ~1.4 (≈ #2) |
| 10" | ~3.0 | ~2.1 (≈ #3) |
| 12" | ~5.0 | ~3.6 (≈ #5) |
| 14" | ~7.0 | ~5.0 (≈ #7) |
| 15–16" | ~10.0 | ~7.1 (≈ #10) |
| 17–18" | ~14.0 | ~10.0 (≈ #15) |
| 20" | ~20.0 | ~14.2 (≈ #20) |
| 24" | ~25–30 | ~18–21 (≈ #25–#30) |
| 28" | ~40–50 | ~28–36 (≈ #40–#50) |
| 32" | ~65–70 | ~46–50 (≈ #65–#70) |
Tips for Choosing the Right Pot Size
- Choose a pot 1–2 inches larger in diameter than your plant’s current root ball.
- Deeper pots hold more soil and moisture—better for large-rooted plants.
- Shallow pots dry faster and suit succulents, bromeliads, and orchids.
- When in doubt, size up—especially for fast-growing tropicals.
Friendly note: These are typical nursery approximations. Actual volume may vary by pot depth, shape, and manufacturer.