Seed Spacing Calculator
How many plants fit in your bed? Enter the bed size and plant spacing to get an exact plant count â no overcrowding, no wasted space.
Calculate your plant count
Use the mature plant spacing from your seed packet.
Square-foot gardening basics
The idea behind this calculator comes from square-foot gardening: divide a bed into a grid and give every plant exactly the space it needs â nothing more. Instead of traditional wide rows with walking paths between them, you space plants evenly in both directions across the whole bed. The result is dramatically higher yields per square foot, fewer weeds (the leaf canopy shades the soil), and less wasted space.
The math is simple. Convert the bed to inches, then divide each dimension by the plant spacing and round down: a 4Ã8 ft bed (48 à 96 inches) at 12-inch spacing gives 4 rows à 8 plants = 32 plants. The calculator does this for you and shows the row breakdown so you can lay out the grid.
Use mature spacing, not seedling size
The single most important rule: space for the adult plant, not the seedling. A tomato seedling is two inches tall; the mature plant needs 18â24 inches. Crowded mature plants compete for light, water and nutrients, stay stunted, and trap humidity that invites fungal disease. Always use the "thin to" or "final spacing" number on the seed packet â never the seed-sowing depth or the size of the transplant in front of you.
| Crop | Typical spacing | Per 4Ã8 ft bed |
|---|---|---|
| Carrots, radishes | 3 in | ~512 |
| Lettuce, spinach | 6 in | 128 |
| Bush beans | 4â6 in | ~128â192 |
| Peppers, eggplant | 12â18 in | ~15â32 |
| Tomatoes (caged) | 18â24 in | ~12â16 |
| Broccoli, cabbage | 12â18 in | ~15â32 |
| Zucchini / squash | 24â36 in | ~4â8 |
These are starting points â varieties differ, so check your specific seed packet. Vining crops like cucumbers and pole beans can be trellised vertically to save enormous amounts of bed space.
How the calculator lays out rows
The calculator divides the bed width by the spacing to get the number of rows, and the bed length by the spacing to get plants per row, rounding down in both cases so every plant gets its full spacing. The leftover inches become margin around the edges â aim to center the grid so the margin is split evenly on both sides rather than leaving one wide strip.
For very small spacings (under 4 inches), many gardeners skip strict rows and broadcast-sow or use a grid pattern, which the row breakdown still approximates well enough for planning seed quantities.
Succession planting: harvest all season
Knowing how many plants fit is only half the plan â the other half is when to plant them. Fast crops like lettuce, radishes, arugula and bush beans can be sown every 2â3 weeks for continuous harvests instead of a single glut. And as soon as a spring crop finishes, replant that space with a summer crop: peas out, beans in; lettuce out, peppers in.
A good rhythm: each time you harvest a square, tuck in the next sowing or transplant the same day. Your bed never sits empty, and the calculator tells you exactly how many seeds or starts each replanting needs.
Spacing tips
- Give air circulation priority. In humid climates, space at the wide end of the packet range â airflow prevents blight and mildew.
- Interplant fast and slow crops. Radishes (3-inch spacing, 25 days) can grow between slow carrots in the same row and be gone before the carrots need the space.
- Trellis vertically. Cucumbers, pole beans and indeterminate tomatoes grown up use a fraction of the bed footprint.
- Don't forget paths. The calculator assumes you reach the bed from the edges â keep beds 4 ft wide or less so you never have to step on the soil.
Frequently asked questions
How many plants fit in a 4x8 raised bed?
It depends on spacing: 32 plants at 12-inch spacing (4 rows à 8), 128 at 6-inch spacing, about 15 at 18-inch spacing. Enter your crop's mature spacing in the calculator for an exact count.
Should I use seed spacing or mature plant spacing?
Always use the mature (final) spacing from the seed packet. Crowded mature plants compete for light, water and nutrients, grow poorly, and invite disease.
What is square foot gardening spacing?
Divide beds into 1-foot squares: 16 plants per square at 3-inch spacing (carrots), 9 at 4-inch (bush beans), 4 at 6-inch (lettuce), or 1 at 12-inch (peppers, broccoli).
How far apart should rows be in a vegetable garden?
Traditional row gardens use 18â36 inch rows for walking paths. In raised beds you never step on, use the plant spacing in both directions and skip wide rows.
What is succession planting?
Sowing fast crops every 2â3 weeks (lettuce, radishes, bush beans) for continuous harvests, and replanting each space as soon as a crop finishes.