How does the square-grid formula work?

Plants in a row = floor(bed length ÷ spacing); rows = floor(bed width ÷ spacing); total = rows × plants-per-row. Each plant occupies a square cell of side equal to the spacing, so the formula is simply floor(L/s) × floor(W/s).

What is a triangular (offset-row) planting pattern?

Alternate rows are shifted sideways by half a spacing, so each plant sits in the gap between the two plants in the row above it — the same arrangement as a hexagonal grid. The row pitch (vertical distance between rows) is spacing × √3 ÷ 2 ≈ 0.866 × spacing. This is the most space-efficient pattern possible on a flat surface and fits roughly 15 % more plants than a square grid at the same inter-plant spacing.

How much more efficient is the triangular pattern?

A perfect infinite triangular grid is about 15.47 % denser than a square grid at the same spacing. In practice, the gain depends on bed shape: very narrow or short beds may gain less because fewer extra plants fit in the staggered rows. The calculator shows the exact difference for your dimensions.

What does "plants per m²" mean and why does it matter?

Density tells you how intensively you are planting. Crops like carrots tolerate 150–400 plants/m²; brassicas need as few as 3–5/m². Comparing your density to the reference table at the bottom of the calculator lets you quickly spot if you are overcrowding or under-using your space.

Can I use feet and inches?

Yes. Click the "in" or "ft" unit button and all three inputs convert to that unit instantly. The calculator uses centimetres internally and displays both metric and imperial results.

Does spacing mean the gap between plants or centre-to-centre distance?

Centre-to-centre distance — which is what seed packets and nurseries give. If a packet says "space 30 cm apart" it means 30 cm from the centre of one plant to the centre of the next, not 30 cm of bare soil between them.

Plant Spacing Calculator

A plant spacing calculator that tells you exactly how many plants fit into any rectangular bed — and whether a square or triangular (offset-row) layout makes better use of your space. It handles any unit (cm, in, ft, m), converts on the fly, and draws a dot-grid diagram so you can visualise the layout before you pick up a trowel.

How it works

The two supported patterns use different formulas.

Square grid

Every plant sits at the corner of a grid of equal squares. The number of plants is simply:

Plants = floor(L ÷ s) × floor(W ÷ s)

where L is the bed length, W is the bed width and s is the centre-to-centre spacing. Each plant “owns” a square cell of side s, so the area per plant is s².

Triangular (offset-row) grid

Alternate rows are shifted by half a spacing (s ÷ 2). The vertical distance between rows shrinks to:

row pitch = s × √3 ÷ 2 ≈ 0.866 × s

Each plant now sits at the centre of a regular hexagon, the tightest possible packing on a flat surface. The number of rows is:

rows = floor((W − s) ÷ row pitch) + 1

Odd-numbered rows start at x = 0 and hold floor(L ÷ s) + 1 plants (capped at the bed edge); even rows are offset by s ÷ 2 and may hold one fewer. The calculator counts each row individually for precision.

The density gain over square packing is exactly 2 ÷ √3 − 1 ≈ 15.47 % for a large infinite bed; real-world gains for finite beds are shown in the results panel.

Worked example

A raised bed 240 cm × 120 cm planted with lettuce at 25 cm spacing:

Pattern	Plants	Density
Square grid	9 × 4 = 36	12.5 /m²
Triangular	43	14.9 /m²

The triangular layout adds 7 extra lettuces in the same space — a useful gain when growing in limited raised-bed area.

A 4 ft × 8 ft bed with basil at 8 in spacing (square-foot gardening style):

Square grid: 6 × 12 = 72 plants
Triangular: 83 plants (+15 %)

Switch the unit selector to “in” or “ft” to enter values directly; the calculator converts to cm internally.

Formula reference

Symbol	Meaning
L	Bed length (same unit as s)
W	Bed width
s	Centre-to-centre plant spacing
floor(x)	Round down to nearest whole number
√3	≈ 1.732 (exact)

The coverage percentage shown in the results is the ratio of the total plant cell area to the bed area. For a square grid this is always (floor(L/s) × s × floor(W/s) × s) ÷ (L × W); for a triangular grid each plant cell is an equilateral triangle of side s with area (√3 ÷ 4) × s², and coverage = total plants × cell area ÷ bed area.