Allocate square feet to each plant and see exactly how many plants you can fit using Mel Bartholomew's SFG method.
Total squares: 16 | Used: 0 | Remaining: 16
Enter the number of squares to allocate to each plant (0 = not planting):
Square foot gardening (SFG) was developed by Mel Bartholomew, a retired efficiency engineer who published the original "Square Foot Gardening" book in 1981 after realizing that traditional row gardening wasted enormous amounts of space, water, and effort on paths and single-row planting. The core insight is simple: instead of planting in rows with wide gaps designed for mechanical cultivators, you divide a raised bed into a grid of 1-foot squares and plant each square at the maximum density the crop can support. A 4x4 raised bed has 16 squares. A 4x8 bed has 32 squares. Each square gets exactly one crop, with the number of plants per square determined by the plant's spacing requirements — 1 plant for large crops like broccoli, 4 for lettuce, 9 for beans, and 16 for carrots or radishes.
The method produces dramatically more food per square foot than traditional row gardening — Bartholomew claimed up to 10x more yield per unit of space — because the intensive spacing shades out weeds (reducing weeding labor by 90%), and the raised beds with quality soil mix (Mel's Mix: 1/3 compost, 1/3 peat moss or coco coir, 1/3 coarse vermiculite) are never compacted by foot traffic. The 4-foot bed width is not arbitrary — it ensures you can reach the center of the bed from both sides without stepping in it, preserving the loose, aerated soil structure that makes the method work.
The spacing system in SFG is derived from each plant's recommended spacing. A plant that needs 12 inches of space in all directions gets 1 per square. A plant that needs 6-inch spacing gets 4 per square (2 columns x 2 rows within the 12x12 space). One that needs 4-inch spacing gets 9 per square, and 3-inch spacing yields 16 per square. This calculator applies exactly those ratios. Large plants like tomatoes (18–24 inches) and zucchini (24–36 inches) take more than one square — tomatoes need 1 square with a cage and zucchini typically consumes 4 squares (2x2).
Companion planting within the SFG framework is straightforward: plant heavy feeders next to light feeders, and use pest-repelling plants as border crops. Basil planted adjacent to tomatoes is the most well-known companion pair — basil is said to repel aphids and thrips and may improve tomato flavor. Marigolds as border plants deter whiteflies and nematodes. Tall crops like pole beans and cucumbers should be trellised on the north side of the bed (in the northern hemisphere) so they don't shade lower crops; they can often be planted in the same 1-foot square as a compact companion.
The plants-per-square formula is based entirely on recommended plant spacing: 1 plant per square for crops needing 12" spacing (broccoli, cabbage, kale, pepper, eggplant); 2 per square for those needing 6" spacing when planted in an offset pattern (chard, parsley); 4 per square for 6" spacing in a grid (lettuce heads, basil); 9 per square for 4" spacing (bush beans, beets, spinach, garlic); and 16 per square for 3" spacing (carrots, radishes, onion sets, turnips). Larger crops like tomatoes (1 per 2x2 area = 0.25 per square foot) and zucchini (0.25 per square foot) require reserving multiple squares. This calculator applies these ratios directly and shows you total plant count for however many squares you allocate.
A 4x4 bed gives you 16 squares to work with, which is plenty for a productive kitchen garden. A classic beginner layout might allocate: 1 square for a tomato plant (with cage), 1 for a pepper, 2 for bush beans (18 plants), 2 for lettuce (8 heads), 1 for basil, 1 for parsley, 2 for carrots (32 carrots), 1 for radishes (16), 1 for beets (9), and 4 squares for cucumbers on a trellis along the north edge. That leaves no squares unused and provides fresh salads, sauce tomatoes, and pickles from a 16-square footprint. The key mistake beginners make is allocating 4 squares for zucchini — one plant produces prolifically and one square is plenty, freeing the other three for something else.
The spacing recommendations are guidelines based on plants' mature canopy size, not hard rules. Spacing them tighter than recommended reduces per-plant yields (smaller heads of lettuce, smaller beets) but does not kill plants — some experienced SFG gardeners deliberately over-plant lettuce and spinach for cut-and-come-again harvests. Spacing them wider than recommended wastes bed space without improving yields significantly for most crops. Where the spacing matters most is for large fruiting crops: tomatoes, peppers, and cucumbers planted too tightly compete for light and airflow, which directly increases disease pressure and reduces fruit set. For root vegetables, overcrowding prevents proper root development — carrots planted 2 inches apart instead of 3 inches will be thin and forked.
The most productive layout places the tallest plants — trellised cucumbers, pole beans, and peas — along the north edge of the bed so they don't shade shorter plants. Heat-loving crops (tomatoes, peppers, basil) go in the sunniest, most central position. Fast-maturing crops (radishes, lettuce, spinach) go in squares where you plan to succession plant — after radishes finish in 30 days, replant the square with a second crop. Group plants with similar water needs: cucumbers and squash need more water than tomatoes and peppers, so placing them near the same drip emitter or hand-watering zone simplifies irrigation. Leave at least one square on each end free if you plan to run a trellis, as the trellis posts need anchor room.
Standard indeterminate tomato varieties (like most heirloom and beefsteak types) need 18–24 inches of clearance in all directions and are typically planted at 1 plant per 4 square feet (2x2 grid allocation) in a raised bed. Determinate (bush) varieties like Patio, Celebrity, or Roma can be squeezed to 1 plant per 2–3 square feet. In practice, most SFG gardeners cage a single indeterminate tomato in a 2x2 corner of the bed and prune to 2–3 main stems to keep the plant manageable. One indeterminate plant caged and pruned can produce 15–30 pounds of fruit in a season from a 4-square footprint — there is rarely a reason to plant more than 1–2 tomatoes in a single 4x8 bed unless you are canning intensively.
Vertical growing is one of the most effective ways to multiply the productivity of an SFG bed. A sturdy 5–6 foot trellis along the north edge of a 4x8 bed can support 8 cucumber plants, 16 pole bean plants, or an entire row of sugar snap peas in a single 1-foot-wide strip — crops that would otherwise sprawl across 8–12 square feet of bed space. Wire cattle panel (16 feet long, 52 inches tall) bent into an arch over two parallel beds creates a walk-through tunnel that grows cucumbers, melons, and winter squash overhead, leaving the ground-level squares free for shade-tolerant crops like lettuce and spinach. Vertical growing works best with crops that naturally climb (peas, beans, cucumbers) or that can be trained with clips (tomatoes, melons). Always anchor trellises firmly — a full cucumber vine in summer wind creates significant load.