Plant Spacing Grid Calculator

Plant spacing calculations determine how many plants fit in a garden bed and how far apart to set them, balancing air circulation, root competition, light, and yield per square foot.

Core formulas:

Row planting (rectangular grid): Plants per row = Bed Length ÷ Spacing Number of rows = Bed Width ÷ Row Spacing Total plants = Plants per row × Number of rows

Both are rounded down. It is tempting to add one to each, on the reasoning that a 8 ft row at 12-inch spacing has nine positions if you count both ends, and plenty of calculators do exactly that. It is the fence-post formula and it is wrong here, because a plant is not a fence post. Each one needs half its spacing of clear ground on every side, so the outermost plants sit half a spacing in from the bed edge, not on it. Add one per row and one per column and a 4 × 8 bed comes out at 45 basil plants when it actually holds 32.

Square foot gardening method: Plants per square foot = (12 ÷ Recommended Spacing)² (where spacing is in inches)

Triangular/offset planting (about 15% more plants): Row spacing = Recommended Spacing × 0.866 (the sine of 60°)

Offsetting alternate rows lets you pull the rows closer without any two plants ending up nearer than the spacing you asked for, because the diagonal neighbours take up the slack. It is free yield and it costs nothing but a tape measure.

Common vegetable spacing guide:

Worked example: A 4 ft × 8 ft raised bed, planting basil at 12-inch spacing: Plants per row = 8 ÷ 1 = 8 plants Number of rows = 4 ÷ 1 = 4 rows Total = 8 × 4 = 32 basil plants

Which is exactly what the square foot gardening column above predicts: basil is 1 per square foot, and the bed is 32 square feet. When two methods agree, the number is probably right.

Offset the alternate rows and the row spacing drops to 12 × 0.866 = 10.4 inches, which fits a fifth row into the same 4-foot width. That is 37 plants from the same bed.

Too dense vs. too sparse: plants crowded together compete for water and nutrients and hold humidity around their leaves, which is how powdery mildew gets started. Plants spread too far waste bed space and let weeds into the gaps. Square foot gardening lands close enough to right for most crops that it is worth using as a default and only deviating when a plant tells you otherwise.