How to measure for your square foot garden project
- Enter your bed dimensions. Type the length and width of your raised bed in feet. A 4 x 4 bed is the classic square-foot-gardening starter size, but 4 x 8 and 4 x 12 are common stretches. The calculator converts the area into one-foot squares automatically.
- Pick a crop or a themed kit. Choose a single crop to fill the whole bed, or select a salsa, pizza, herb, or salad kit. Each kit divides the bed into crop sections using the square-foot-gardening rule: 1 plant per square for large crops like tomato and pepper, 4 for medium crops like lettuce and basil, 9 for small crops like onion and spinach, and 16 for tiny-seeded crops like carrot and radish.
- Read the plant counts and buy soil. The result shows total plants and a per-crop breakdown, plus the cubic feet of soil and the number of 1.5 cu ft bags needed to fill the bed at your chosen depth. Buy transplants for tomatoes and peppers; start greens, roots, and herbs from seed directly in the square.
How the square foot garden calculator works
Square-foot gardening divides a raised bed into a grid of one-foot squares. The total number of squares equals length (ft) x width (ft). Each square holds a fixed number of plants based on crop size: 1 for large plants, 4 for medium, 9 for small, and 16 for tiny. For a single crop the math is: plants = squares x plants-per-square. For a themed kit, the 16 base squares are split between crops in the same proportions, then scaled up or down for beds larger or smaller than 4 x 4. Soil volume is length x width x depth (in inches / 12) in cubic feet; divide by 1.5 to get the number of standard compressed-mix bags. Example: a 4 x 8 salad kit has 32 squares; lettuce gets 6/16 of them = 12 squares x 4 plants = 48 lettuce; spinach gets 5/16 = 10 squares x 9 = 90 spinach; carrot gets 3/16 = 6 squares x 16 = 96 carrots; radish gets 2/16 = 4 squares x 16 = 64 radishes; total 298 plants.
Which type are you estimating?
Salsa garden kit (tomato, pepper, onion, cilantro)
Divide the bed into four equal crop zones: tomatoes (1 per sq), peppers (1 per sq), onions (9 per sq), and cilantro (9 per sq). In a 4 x 4 bed the kit yields 4 tomatoes, 4 peppers, 36 onions, and 36 cilantro for a total of 80 plants. Scale up to a 4 x 8 bed and the count doubles to 160.
Enter: Plan: Salsa garden kit; bed 4 x 4 ft minimum
Pizza garden kit (tomato, basil, pepper, onion)
A culinary classic: tomatoes and peppers at 1 per square, basil at 4 per square, and onions at 9 per square, each getting a quarter of the bed. In a 4 x 4 bed: 4 tomatoes, 16 basil, 4 peppers, 36 onions = 60 plants. Basil planted next to tomatoes is also a classic companion planting.
Enter: Plan: Pizza garden kit; bed 4 x 4 ft minimum
Herb garden kit (basil, parsley, cilantro, chives)
All four herbs fit 4 per square (basil, parsley) or 9 per square (cilantro) or 16 per square (chives). A 4 x 4 herb bed yields 16 basil, 16 parsley, 36 cilantro, and 64 chives. Snip-and-come-again; plant from seed or transplants depending on availability.
Enter: Plan: Herb garden kit; bed 4 x 4 ft, soil depth 6 in
Salad garden kit (lettuce, spinach, carrot, radish)
Fast-maturing crops for continuous harvests. Lettuce (4 per sq) gets 6 of 16 squares; spinach (9 per sq) gets 5; carrot (16 per sq) gets 3; radish (16 per sq) gets 2. In a 4 x 4 bed: 24 lettuce, 45 spinach, 48 carrots, 32 radishes = 149 plants. Succession-sow radishes every 2 weeks for a steady supply.
Enter: Plan: Salad garden kit; bed 4 x 4 ft, soil depth 8 in for carrots
Single-crop mode
Fill the whole bed with one crop. A 4 x 4 bed holds 16 tomatoes or peppers (1 per sq), 64 lettuce (4 per sq), 144 onions or spinach (9 per sq), or 256 carrots or radishes (16 per sq). Useful for succession planting: sow one half of a 4 x 8 bed this week and the other half three weeks later.
Enter: Plan: pick any single crop; any bed size
Tips & ways to save
- Always buy transplants for tomatoes and peppers — starting from seed indoors takes 6-8 weeks. Start greens, roots, and herbs directly from seed in the square.
- Mel's Mix (equal parts compost, peat moss or coir, and coarse vermiculite) drains well and never needs tilling — ideal for the 6-inch or deeper beds the calculator recommends.
- Succession-plant radishes, lettuce, and spinach every 2-3 weeks; as one square is harvested, direct-sow a new batch so you harvest continuously rather than all at once.
- Keep the grid visible: lay bamboo stakes or string along the one-foot lines so you plant precisely and avoid overcrowding, which is the most common square-foot-gardening mistake.
- A 4 x 4 bed filled 6 inches deep needs 8 cu ft of soil (about 6 bags of 1.5 cu ft mix). Add 2-3 inches each season by top-dressing with compost rather than replacing the whole bed.
Plants per square foot
| Plants / sq ft | Crops |
|---|---|
| 1 | Tomato, pepper, broccoli, cabbage, kale |
| 4 | Lettuce, basil, parsley, swiss chard |
| 9 | Spinach, onion, cilantro, beet, bush bean |
| 16 | Carrot, radish, chives |
A 4×4 bed is 16 one-foot squares. A 4×8 bed is 32. Multiply the per-square count by your number of squares: e.g. 16 squares of lettuce = 64 plants.
Frequently asked questions
How many plants fit in a 4x4 raised bed?
What plants go in a salsa garden?
How much soil do I need for a square foot garden?
What is the difference between square-foot gardening and row gardening?
How many plants fit in a 4x8 raised bed?
Can I use square-foot gardening in containers or grow bags?
Sources
Related calculators
Reviewed by the BackyardCalc editorial team. Figures are computed from the formula above and checked against manufacturer yields.