What Is Plant Spacing?
Spacing is the gardener's oldest tradeoff: too tight and plants compete for light, water, and airflow (hello, powdery mildew); too loose and the bed wastes weed-friendly bare soil. Once you've settled a spacing, the immediate question is purely arithmetic — how many transplants to raise or buy for the bed you actually have.
Enter the bed dimensions and your chosen spacing, pick square rows or the offset pattern, and get the count with the row-by-row layout. Buy a couple of spares beyond the number — transplant casualties are part of gardening — and run mixed beds one crop-section at a time.
Finishing the bed after planting? Depth and bags math is in the Mulch Calculator.
How to Calculate Plant Spacing: Square vs Triangular
Same spacing, two geometries:
Square: plants = ⌊L ÷ s⌋ × ⌊W ÷ s⌋ Triangular: row gap = s × 0.866, alternate rows offset by s/2 → ≈ 15% more plants in the same bed
Worked example: an 8 × 4 ft bed at 12″ spacing fits 32 plants in square rows (8 × 4), or 38 triangular — five offset rows alternating 8 and 7. The plant-to-plant distance is identical; the packing is just smarter.
Plant Spacing Chart: Plants per Square Foot
Square-grid density at the common spacings (the square-foot-gardening numbers) — 144 ÷ spacing²:
| Spacing | Plants per sq ft | Typical crops |
|---|---|---|
| 3″ | 16 | Carrots, radishes, green onions |
| 4″ | 9 | Beets, spinach, bush beans |
| 6″ | 4 | Lettuce heads, chard, parsley |
| 12″ | 1 | Peppers, basil (full), strawberries |
| 18″ | 1 per 2.25 sq ft | Tomatoes (staked), broccoli, cabbage |
| 24″ | 1 per 4 sq ft | Zucchini, bush squash, determinate tomatoes |
These densities assume good soil and irrigation — intensive spacing feeds and waters more per square foot precisely because the roots share it.
How to Read Spacing on a Seed Packet
Seed packets give two numbers — in-row spacing and between-row spacing (say, 4″ apart in rows 18″ apart). The wide row gap exists for walking and hoeing in field-style gardens; raised beds you never step in can use the tighter equal-grid spacing this calculator models, which is the entire premise of intensive and square-foot methods.
Tags mean mature size: an 18″ spacing on a tomato seedling looks absurd in May and correct in July. Crowding shows up late as disease pressure and small yields, so when torn between two spacings, the wider one usually wins — or split the difference with the triangular pattern, which buys density without cutting plant-to-plant distance.