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Plant Spacing Calculator

Calculate how many plants fit in a rectangular bed using standard grid spacing or the Square Foot Gardening density method.

Plant count
Enter bed dimensions, plant spacing, and the Square Foot Gardening density to get plant counts for both methods.

Sets bed size and spacing.

Bed dimensions
ft

Interior length of the bed. Enter in ft, in, m, or cm.

ft

Interior width of the bed.

Spacing
in

Distance between plants in a grid, center to center. Switch to cm for metric. Use the recommended spacing from the seed packet or plant tag.

Square Foot Gardening density: number of plants per square foot in a 1-ft grid. SFG standard options: 1 (large plants such as tomatoes), 4 (medium such as lettuce), 9 (small such as spinach), 16 (tiny such as radishes).

Grid count (edge-inclusive)

35 pcs

SFG count: 24 pcsColumns: 7 pcsRows: 5 pcs

What is plant spacing and which method should I use?

Grid spacing counts edge-to-edge plants in a rectangular array; Square Foot Gardening assigns a fixed density per 1-ft square.

Plant spacing describes how far apart plants are placed, center to center, within a bed. The count in a given area depends on the spacing and on which planting method you use.

Grid spacing (standard spacing) treats the bed as a rectangular array and counts plants at the edges as well as the interior. A 3-foot row with plants every 6 inches holds plants at 0, 6, 12, 18, 24, 30, and 36 inches – seven plants. The formula counts floor(length / spacing) + 1 positions per axis, then multiplies for both axes.

Square Foot Gardening (SFG), developed by Mel Bartholomew, divides the bed into 1-foot squares and assigns a density by plant size: 1, 4, 9, or 16 plants per square foot. SFG gives a lower count than grid spacing for most configurations because it rounds the bed dimensions down to whole feet before computing.

Both methods are useful. Grid spacing is more precise for beds where you want exact plant placement. SFG is faster for planning and purchasing seeds.

How to calculate plant count

The edge-inclusive grid formula, how floor is encoded, and how SFG count differs from grid count.

Formula

grid count = (floor(length/spacing)+1) x (floor(width/spacing)+1); SFG count = floor(length_ft) x floor(width_ft) x density

Grid count (edge-inclusive)

Columns = floor(bed length / spacing) + 1. Rows = floor(bed width / spacing) + 1. Grid count = columns x rows. The +1 adds the edge plant at each axis; without it, a 3-ft row with 6-in spacing would give floor(3 ft / 0.5 ft) = 6 intervals but 7 plants (at positions 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 ft).

All lengths and spacings are converted to the same store unit (inches) before computation. Enter bed dimensions in feet, inches, meters, or centimeters; enter spacing in inches or centimeters.

SFG count

SFG count = floor(bed length in ft) x floor(bed width in ft) x density. Only whole 1-ft squares are counted. A 3.5 x 2.5 ft bed has 3 x 2 = 6 usable squares; the half-foot margin is reserved.

Why grid count is usually higher

Grid spacing places plants at exact intervals across the entire bed including edges. SFG rounds down to whole 1-ft sections and counts from a fixed grid, so the counts diverge more as bed dimensions include fractional feet.

Metric

Bed dimensions may be entered in meters or centimeters. Spacing may be entered in centimeters. The calculator converts to inches before computing.

Example

A 3 x 2 ft bed, 6 in plant spacing, SFG density 4:
  1. 1
    Columns (length axis)floor(36 in / 6 in) + 1 = 6 + 1 = 7
  2. 2
    Rows (width axis)floor(24 in / 6 in) + 1 = 4 + 1 = 5
  3. 3
    Grid count7 x 5 = 35 plants
  4. 4
    SFG count (3 x 2 ft bed, 4/sq ft)floor(3) x floor(2) x 4 = 3 x 2 x 4 = 24 plants
Result35 plants (grid) / 24 plants (SFG)

FAQ

What is the difference between grid spacing and Square Foot Gardening?

Grid spacing (standard spacing) places plants at equal distances in a rectangular grid and counts edge plants: a 3-ft row with 6-in spacing fits plants at 0, 6, 12, 18, 24, 30, 36 inches, giving 7 plants. SFG simplifies planning by dividing the bed into 1-ft squares and planting a fixed number per square based on plant size. SFG gives a conservative (lower) count for most configurations because it rounds down to whole 1-ft sections.

Where do I find the recommended spacing for a plant?

The seed packet, plant tag, or catalog description lists the recommended in-row spacing. This is the center-to-center distance between plants, not the row-to-row distance. For the SFG method, use the plant's spacing to look up the corresponding density: 12-in spacing = 1 per sq ft; 6-in = 4 per sq ft; 4-in = 9 per sq ft; 3-in = 16 per sq ft.

Can I enter metric dimensions?

Yes. Switch bed length and width to meters or centimeters using the unit picker. Switch spacing to centimeters. The calculator converts internally to inches before computing; the plant counts are the same regardless of which unit you use.

Sources

High-trust standards and documented references.

  1. 1. Square Foot Gardening, 2nd Edition

    Square Foot Gardening Foundation

    Defines the SFG density table (1/4/9/16 plants per square foot by plant size) and the 1-ft grid planting method used in the sfgCount calculation.

    https://www.squarefootgardening.org/

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