Seed Spacing Calculator
Seeds per row
8
How it works
Correct seed spacing ensures each plant gets adequate light, water, and nutrients without competition. Too close and yields drop; too far and space is wasted. The Seed Spacing Calculator converts seed packet spacing instructions into a total plant count for any bed size.
**Row vs. square-foot spacing** Traditional row gardening wastes space between rows. Square-foot gardening plants in a grid at the closest recommended spacing in all directions. At 6-inch spacing in a 4x4 foot bed: 8x8 = 64 plants per 16 square feet. At 12-inch spacing: 4x4 = 16 plants per 16 square feet.
**Common vegetable spacings** Carrots and radishes: 2 to 3 inches. Lettuce and spinach: 4 to 6 inches. Beets and onions: 4 inches. Peppers and eggplant: 12 to 18 inches. Tomatoes: 18 to 36 inches. Winter squash and pumpkins: 24 to 48 inches. Corn: 12 inches in-row, 30 inches between rows for pollination.
**Thinning** Many seeds are planted more densely than final spacing and thinned after germination. Plant 2 to 3 carrot seeds per inch and thin to one every 3 inches. Thinning is easier than transplanting and ensures the strongest plants survive.
**Companion planting** Interplanting fast-maturing crops like radishes and lettuce between slow crops like tomatoes and peppers maximizes bed productivity and space usage.
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Frequently Asked Questions
- Plants compete for light, water, and nutrients. The result depends on the crop: tomatoes and peppers planted too close (under 18 inches) develop poor air circulation, increasing disease risk (blight, mildew) and reducing fruit size. Root vegetables (carrots, beets) that are too crowded develop forked, stunted, or deformed roots because there's no room for them to expand. Leafy greens and herbs are more tolerant of close spacing — 'cut and come again' harvest compensates for crowding. In all cases, crowded plants produce lower total yield per plant (but sometimes acceptable yield per square foot if harvested early).
- Square-foot gardening (SFG) works best for most vegetables and is efficient for small gardens. Standard SFG grid is 12-inch squares: 1 plant per square for tomatoes, peppers, broccoli; 4 per square for lettuce, Swiss chard; 9 per square for spinach, bush beans; 16 per square for carrots, onions, radishes. SFG doesn't work as well for corn (needs at least a 4×4-foot block for wind pollination), vining crops like winter squash and watermelon (need much more space), or asparagus (perennial that needs permanent bed). For these, follow traditional row spacing.
- No — most seeds are planted at higher density and thinned after germination. Germination rates are never 100%, and not all seedlings will be equally vigorous. Standard practice: plant 2–3 seeds per desired plant location, then thin to the strongest single seedling once they're 1–2 inches tall. For very expensive or rare seeds (certain heirloom varieties, F1 hybrids), you might plant 1 seed per location and accept imperfect germination. For direct-sown root vegetables like carrots, broadcast seed at 3–4x the final desired spacing and thin after germination — transplanting damages tap roots.
- In containers, you can sometimes push spacing slightly tighter (10–15%) because you control irrigation and fertilization precisely, eliminating the resource competition that makes ground spacing necessary. However, root volume is strictly limited by container size — root-bound plants stop producing. For tomatoes: 5-gallon minimum per plant, 15-gallon for indeterminate types. For peppers: 3–5 gallon per plant. Dwarf and patio varieties bred for containers tolerate much tighter spacing. For lettuce and herbs in containers, standard SFG spacing works well. Never plant more than one large plant per container — companionship doesn't help in containers the way it does in ground beds.