Container Garden Calculator
Plan your container vegetable garden. Calculate soil volume, plants per pot, and whether your containers are the right size.
Container gardening is perfect for patios, balconies, and small spaces. A standard 12-inch pot holds about 5 gallons of soil and works for most vegetables. Larger plants like tomatoes and peppers do best in 5-gallon (12-inch) or bigger containers, while herbs and radishes thrive in pots as small as 6 inches across.
Data last updated: March 2026
Large (5+ gallon, 12"+ diameter) recommended
Your Container Garden Plan
Detailed Breakdown
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Built-in water reservoir keeps plants hydrated. Great for busy gardeners and hot climates.
Frequently Asked Questions
Tomatoes need a minimum 5-gallon container with at least a 12-inch diameter. For best results, use a 10 to 15-gallon container, which gives roots more room and retains moisture better. Determinate (bush) varieties are better suited to containers than indeterminate (vining) types. Always provide a cage or stake for support, and expect to water daily in hot weather.
How This Calculator Works
This calculator uses standard cylinder volume formulas (pi x radius squared x depth) to determine soil volume in gallons and cubic feet. Plant capacity is estimated by comparing each vegetable's recommended spacing to the usable planting area of the container (roughly 70% of total surface area, accounting for edge buffer). Container size requirements are based on root depth and spread needs: large fruiting plants like tomatoes need at least 5 gallons, medium crops like lettuce need 3 gallons, and compact plants like radishes grow fine in 1-gallon pots.
Tips for Container Gardening Success
- Always use potting mix, not garden soil. Potting mix is lighter, drains better, and is free of weed seeds and diseases.
- Ensure every container has drainage holes. Sitting water causes root rot, which is the most common reason container plants die.
- Containers dry out faster than garden beds. During summer heat, you may need to water twice daily. Consider self-watering pots or drip irrigation.
- Feed container vegetables every 2 to 3 weeks with a balanced liquid fertilizer. Nutrients leach out with each watering.
- Group containers by water needs. Place thirsty plants like tomatoes together and drought-tolerant herbs separately.
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