When planning a small outdoor plant box, choosing the right dimensions is crucial for plant health and aesthetic appeal. A typical small plant box should be at least 12 inches (30 cm) deep to allow adequate root growth for most herbs, flowers, and small vegetables. The width can range from 12 to 24 inches (30–60 cm), depending on the number of plants and available space. Length is flexible but keeping it under 36 inches (90 cm) ensures easy mobility.

For optimal drainage, ensure the box has holes at the bottom and stands 1–2 inches (2.5–5 cm) off the ground. Materials like cedar or redwood are ideal for durability and resistance to rot. Place the box in a spot with 6–8 hours of sunlight daily for most plants to thrive. Whether you're DIY-ing or buying, these dimensions will help create a functional and stylish addition to your outdoor space.