A window box is a small bed with big ambitions, and the easiest way to ruin one is to overcrowd it. This window box plant count calculator tells you how many plants fit in your box, either in a staggered zigzag or in a simple grid. Enter the inside length and width of the box, the spacing the plants need and the gap you want from the edge, and it counts the plants for you.
How to use the window box plant count calculator
- Measure the inside of the box in inches, not the outside.
- Enter the plant spacing. Use the plant tag, or the plant database for food crops and herbs.
- Set the edge gap. Two inches keeps stems and leaves from squashing against the sides.
- Compare the layouts. The staggered layout fits a few more plants than a grid.
How the counts are worked out
The calculator subtracts the edge gap from both sides, then counts how many plants fit along the length at your spacing, plus one for the first. For the grid, it does the same across the width. For the staggered layout, each new row sits about 87 percent of the spacing from the last, and every other row is shifted half a space, which lets the plants nest between each other.
Choosing plants for a window box
| Light | Edible options |
|---|---|
| Full sun (6+ hours) | Basil, thyme, oregano, chives, compact tomatoes, lettuce in cool weather |
| Part sun | Parsley, mint, leaf lettuce, radishes |
| Shade | Leaf lettuce, chives and mint, which tolerate less light |
Check how much light the spot gets with the sunlight requirement finder. Mint spreads aggressively, so give it a box of its own.
Tips for window boxes that last
- Drainage is essential. Boxes need holes, and sitting in water rots roots.
- Use potting mix, not garden soil, which compacts in containers.
- Water often. Small volumes dry out quickly, sometimes daily in summer.
- Secure the box. A full, wet box is heavy. Use strong brackets and check them each season.
- Plan the mix of plants with the container garden planner, and work out the potting mix volume with the grow bag volume calculator.
Limits of this tool
This counts plants by spacing only. Some plants grow much wider over time, and trailing plants may need fewer neighbors. When in doubt, plant a little looser than the tool suggests, especially for vegetables, which need room and nutrients.
Frequently asked questions
How many plants fit in a 36 inch window box?
With 6-inch spacing and a 2-inch edge gap, about six in a single row. Enter your own numbers above for exact figures.
What does staggered mean?
Plants are set in alternating rows, each offset by half a space, so they nest together like bricks.
Can I grow vegetables in a window box?
Yes, especially herbs, lettuce, radishes and compact tomatoes, as long as the box is deep enough and gets plenty of sun.
How deep should a window box be?
At least 6 to 8 inches for herbs and lettuce, and deeper for tomatoes or root crops.
How often should I water?
Check daily in warm weather. Water when the top inch of mix is dry.