Seed Spacing Calculator
Calculate how many plants fit in a garden bed from dimensions and plant spacing.
Returns total plant count and seeds to buy for vegetables, flowers, and herbs.
Seed spacing determines how many plants fit in a given garden area and how healthy they grow. Crowded plants compete for light, water, and nutrients, resulting in poor yields, disease, and weak growth. Properly spaced plants produce stronger stems, better airflow, and higher yields per plant.
Formulas: Seeds per Row = (Row Length ÷ Spacing Between Seeds) + 1 Number of Rows = (Bed Width − Edge Clearance × 2) ÷ Row Spacing Total Seeds = Seeds per Row × Number of Rows Square-foot gardening: Plants per Sq Ft = 144 ÷ (Recommended Spacing in inches)²
Standard spacing chart (recommended in-row spacing):
| Vegetable | Spacing | Row Spacing | Depth |
|---|---|---|---|
| Lettuce | 6–12 in | 12–18 in | ¼ in |
| Carrots | 2–3 in | 12–18 in | ¼ in |
| Radishes | 1–2 in | 12 in | ½ in |
| Beans | 3–6 in | 18–24 in | 1–1½ in |
| Peas | 2–4 in | 24–36 in | 1–2 in |
| Corn | 9–12 in | 30–36 in | 1–2 in |
| Tomatoes | 24–36 in | 36–48 in | deep |
| Zucchini | 24–36 in | 36–48 in | 1 in |
| Sunflowers | 6–12 in | 24–30 in | 1 in |
Worked example — raised bed planning: 4-foot wide × 8-foot long raised bed. Growing bush beans. Bean spacing: 4 inches in-row | Row spacing: 18 inches
Seeds per row = (96 inches ÷ 4) + 1 = 24 + 1 = 25 seeds per row Number of rows = (48 inches − 3-inch edges × 2) ÷ 18 = 42 ÷ 18 = 2.3 → 2 rows Total seeds = 25 × 2 = 50 seeds
Buy a packet with 50+ seeds (most bean seed packets contain 100+).
Succession planting: Rather than planting all seeds at once (leading to a glut of harvest), plant ⅓ of your row every 2–3 weeks to stagger the harvest over 6–8 weeks.
Thinning: Many seeds are sown closer than final spacing and then thinned — removing weaker seedlings once they sprout. Always thin rather than transplant — moving seedlings disturbs roots of neighbors.