Square Foot Garden Plants Calculator
Calculate how many plants fit in a square-foot garden grid based on bed size and plants-per-square-foot for each crop.
How to use this tool
- Enter your grid dimensions in feet (standard is 4×4 ft).
- Enter the plants-per-square-foot for your chosen crop.
- The calculator shows total grid squares and the number of plants to buy.
Plan your square-foot garden to grow more food in less space with perfect spacing.
⚠ This tool provides general estimates for education only and is not financial, tax or legal advice. Figures may not reflect your situation — verify with a qualified professional.
Formula
Grid squares = Length (ft) × Width (ft)
Total plants = Grid squares × Plants per square foot
Grid squares are rounded to the nearest integer; total plants is an exact product.
How it works
This calculator applies the square-foot gardening method pioneered by Mel Bartholomew, which divides a raised bed into a grid of one-square-foot cells and assigns a fixed planting density to each cell based on mature plant size. Multiplying the total number of cells by the per-cell density gives the maximum plant count for a given crop.
The plants-per-square-foot value depends on the crop: large plants such as tomatoes or peppers occupy one cell each (1 plant/ft²), medium plants such as lettuce use 4, and small plants such as radishes or carrots use up to 16. Mixing densities across cells requires tracking each section separately.
Worked example
- Bed dimensions: 4 ft × 4 ft. Crop: spinach at 4 plants per square foot.
- Grid squares = 4 × 4 = 16 square feet.
- Total plants = 16 × 4 = 64 plants.
Total grid squares: 16 — Total plants: 64
Common mistakes to avoid
- Using plants-per-square-foot from memory rather than from the seed packet or a verified SFG chart — recommendations vary significantly by variety and source.
- Counting partial squares at the bed edge as full squares, leading to slightly more plants than the bed can support.
- Planning the same plants-per-square-foot for both transplants and direct-sown seeds — direct-sown crops are typically thinned after germination and need the correct final spacing, not seeding density.
Key terms
- Square-foot gardening
- An intensive raised-bed method that divides growing space into 1 ft² sections, each planted to a specific density to maximise yield in small areas.
- Plants per square foot
- A crop-specific density value determined by the plant's mature spread; ranges from 1 (large fruiting crops) to 16 (small root vegetables).
- Raised bed
- A contained planting area filled with amended growing medium, typically 6–12 inches deep, allowing closer plant spacing than in-ground rows.
- Succession planting
- Replanting a finished cell immediately after harvest with a different or the same crop to extend seasonal productivity.
Frequently asked questions
- How many plants per square foot?
- Square-foot gardening uses a simple guide: 1 plant per sq ft for large crops (tomatoes, peppers), 4 for medium (lettuce, basil), 9 for small (spinach, beets), and 16 for tiny crops (carrots, radishes).
- What is square-foot gardening?
- Developed by Mel Bartholomew, square-foot gardening (SFG) divides a raised bed into 1-ft² squares, each planted intensively. It reduces water use, weeding, and wasted space compared to row gardening.