| Variety style | Typical habit | Common target (gal) | Common target (L) | Suggested depth (in) |
|---|---|---|---|---|
| Patio cherry | Dwarf / Patio | 3–5 | 11–19 | 10–12 |
| Roma / paste | Determinate | 7–10 | 26–38 | 12–14 |
| Slicer (bush type) | Determinate | 8–12 | 30–45 | 12–16 |
| Beefsteak (vining) | Indeterminate | 12–20 | 45–76 | 14–18 |
| Large heirloom (vining) | Indeterminate | 15–25 | 57–95 | 16–20 |
- Base volume is chosen by growth habit: dwarf, determinate, or indeterminate.
- Adjustments add or subtract gallons for maturity time, height, climate heat, watering style, and container material.
- Total container volume = per-plant gallons × plants × crowding factor.
- Footprint is derived from: area = (gallons × 231) ÷ depth.
- Round pots use diameter = √(4 × area ÷ π); square pots use side = √(area).
- Select the growth habit that matches your variety label.
- Enter plants per container, then set maturity and height.
- Pick your climate and watering style for realistic demand.
- Choose container shape and material to match your setup.
- Set your planned depth, then press Calculate.
- Use the recommended range; aim for the ideal target.
- Export results as CSV or PDF for easy comparison.
Choosing Pot Volume
Container volume sets the water and nutrient buffer around tomato roots. For dwarf patio types, 10–12 L (3–4 gal) can work, while standard determinate plants usually need 12–20 L (4–5 gal). Vining indeterminate varieties prefer 20–40 L (5–10 gal), especially in hot weeks. Choose at least a 30–35 cm diameter so foliage dries faster after watering. This helps buffer fertilizer salts and prevents midday wilting.
Root Space and Yield
Roots spread near the canopy footprint and rely on air-filled pores. If you expect heavy fruit loads, stay near the upper pot range because steady moisture supports calcium movement to developing fruit. Small pots dry quickly and raise blossom-end rot risk. This calculator scales volume by growth habit, planned soil depth, and a stress factor that covers heat, wind exposure, and missed watering. Expect faster growth in rich mixes.
Drainage and Media Depth
Depth matters as much as liters. Aim for 30–45 cm media depth so feeder roots stay cooler and more oxygenated. Fabric pots and clay dry faster; plastic holds moisture longer, so you can size down slightly. Keep 3–5 cm headspace for watering, add several 6–8 mm drainage holes, and avoid compacted garden soil. Mix 20–30% perlite or bark for structure. Topdress compost monthly for biology.
Watering and Fertility Impact
Watering frequency changes with pot size and season. In 10–12 L containers, daily irrigation is common during fruit set; in 25–40 L containers, intervals often reach two days, depending on sun, mulch, and airflow. Lift the pot to judge weight before refilling. Feed lightly each week, then increase potassium after flowering. Consistent moisture is the main driver of flavor and firmness. Mulch reduces evaporation, stabilizes moisture.
Temperature, Wind, and Support
Site conditions can justify a larger pot even for the same variety. Add 10–25% volume when daytime highs exceed 32°C, when wind is constant, or when containers sit on reflective concrete. A cage or trellis should be anchored without crushing roots; wider pots give safer footing and reduce tipping. If you must use smaller pots, shade the container and prune to one or two stems.
What pot size suits cherry or patio tomatoes?
Most compact cherry or patio varieties do well in 10–12 L (3–4 gal). If the plant is vigorous or you want bigger harvests, move to 15–20 L. Always prioritize drainage and consistent watering.
Can I grow two tomato plants in one container?
It is possible, but only in very large containers. Plan 40–60 L total, strong feeding, and extra staking. Two plants in a small pot compete for water and nutrients and usually yield less overall.
Does pot depth matter if volume is high?
Yes. Tomatoes prefer deep, airy media. Aim for 30–45 cm depth so roots stay cooler and better oxygenated. A wide but shallow pot can still stress plants in heat and during fruit set.
Do fabric pots change the recommended size?
Fabric pots breathe and dry faster, so they often behave like a smaller pot. Choose the upper end of the range and mulch the surface. The payoff is excellent root aeration and less waterlogging risk.
Are self-watering planters a good choice?
They can be, if the reservoir is large and the mix is lightweight. Keep overflow holes clear and avoid leaving water stagnant for days. Monitor salts by flushing occasionally, especially when feeding frequently.
How should I adjust for very hot climates?
Increase pot volume by 10–25%, add mulch, and provide afternoon shade. Water early, then check again in late afternoon. Heat stress is usually a moisture problem, so larger pots and consistent irrigation help most.