Calculate number of plants needed based on bed size and spacing.
The plant spacing calculator returns how many tomato, pepper, lettuce, carrot, or any other crop seedlings fit in a bed of a given size. Enter bed length, bed width, and either a recommended row spacing or square-foot-gardening grid value — the tool returns total plant count and a printable triangular vs square layout comparison. USDA-extension recommendations for common vegetables are listed below as defaults.
Square layout: plants per row = ⌊length / spacing⌋, rows = ⌊width / spacing⌋, total = plants × rows. Triangular (offset) layout: every other row shifted by half-spacing yields ≈ 15% more plants without crowding. The tool also reports recommended spacing for popular crops: tomato 24 in, pepper 18 in, lettuce 8 in, carrot 3 in, basil 12 in. Square-foot-gardening grids (1, 4, 9, 16 per ft²) are also supported.
At 24 inches spacing in a square grid, you fit 8 plants. Switch to triangular spacing and the count rises to 10 plants because every other row offsets by 12 inches.
In a 4×4 ft bed at 8 inches lettuce spacing, square layout returns 36 heads. Stagger sowings every two weeks to keep a continuous harvest from spring through early summer.
A 1 ft × 8 ft strip with 3 inches carrot spacing in a single row gives 32 carrots. Thin to final spacing 7–10 days after germination to give roots room to bulk up.
They follow Cornell, Iowa State, and University of California extension guidelines for home gardens. Commercial growers may use tighter spacing because they have access to drip fertigation and mechanical weeding.
Triangular spacing helps in raised beds and square-foot-gardening where every inch counts. Skip it for crops that need straight rows for mechanical cultivation.
The tool already keeps spacing/2 from each edge so plants do not overhang the frame. If your bed has a slatted wood frame, leave another 2 inches inside to avoid splinters and slow drying-out.