Plant Spacing Math: Plants per Bed, Square-Foot Gardening, and Triangular Layouts
October 29, 2026
The number of plants a bed holds is its area divided by the area each plant needs. For a square grid with spacing s (in inches), each plant takes s² square inches. A 4 by 8 foot bed is 32 square feet, or 4,608 square inches.
At 12-inch spacing, each plant takes 144 square inches (1 square foot), so the bed holds 32 plants. At 6-inch spacing, each plant takes 36 square inches, giving 128 plants. At 3-inch spacing, 9 square inches each, 512 plants.
Skip the math and get your answer instantly:
Open the Area Calculator →Square-Foot Gardening Densities
The square-foot method divides a bed into 1-foot squares and plants a set number per square based on size: 1 per square for large plants (tomatoes, broccoli at 12 inches), 4 for medium plants (lettuce, chard at 6 inches), 9 for small plants (spinach, bush beans at 4 inches), and 16 for the smallest (carrots, radishes at 3 inches). In a 4 by 8 bed, that is 32 tomatoes or 512 carrots, in practice a mix. Follow the seed packet spacing for your variety, and don't overcrowd: tomatoes at 12 inches would be far too tight; they need 18 to 24 inches.
| Spacing | Plants per sq ft | Plants in a 4 x 8 ft bed (square grid) | Example crops |
|---|---|---|---|
| 12 in | 1 | 32 | Broccoli, kale (some) |
| 6 in | 4 | 128 | Lettuce, chard |
| 4 in | 9 | 288 | Spinach, bush beans |
| 3 in | 16 | 512 | Carrots, radishes |
Triangular (Staggered) Spacing
Offsetting alternate rows by half the spacing packs more plants per area. The area per plant at spacing s is 0.866 × s². At 12 inches, that is 0.866 square feet per plant, so a 32-square-foot bed holds 32 ÷ 0.866 = 37 plants, 15% more than the square grid. Edge effects reduce this a bit, since plants near the border use less area. Stagger the plants in drip-irrigated beds to make full use of the space and shade the soil.
Seeds to Sow
Plan for germination: if the seed packet gives 80% germination, sow 1 ÷ 0.8 = 1.25 seeds per desired plant, and thin later. For 128 lettuce plants, sow about 160 seeds. For direct sowing of small seeds, it's common to sow two to three per spot and thin to the strongest. Seeds older than 2 to 3 years germinate less well; test a few on a damp paper towel.
Rows and Paths
Row planting: a 4-foot bed with rows 12 inches apart gives 4 rows; each 8-foot row with 6-inch plant spacing holds 16 plants, so 64 plants, half the density of the square layout because of the empty space between rows. Beds up to 4 feet wide can be reached from both sides; allow 18 to 24 inches for paths. Fertile soil and regular watering support closer spacing.
Frequently Asked Questions
How many plants fit in a 4 by 8 foot bed at 12-inch spacing?
32.
How many carrots at 3-inch spacing?
About 16 per square foot, 512 in 32 square feet.
What is triangular spacing?
A staggered layout that fits about 15% more plants than a square grid.
How many seeds should I sow?
Divide the desired plants by the germination rate.
Should I always plant at the densest spacing?
No, follow the recommended spacing for each crop.