Triangular Plant Spacing Calculator (Offset Rows)

This calculator counts the plants needed to fill a bed or ground-cover area at an even spacing. Enter the area, the spacing between plants and the pattern; a triangular (offset row) pattern fits about 15% more plants than a square grid at the same spacing.

Formula

Area per plant = (spacing ÷ 12)² × pattern factor, in square feet. Plants = area ÷ area per plant, rounded up. On a square grid the factor is 1; on a triangular grid each plant occupies a rhombus of side s and 60° angles, whose area is s² × √3 ÷ 2 = s² × 0.866.

• a: area to fill in square feet
• s: spacing between neighbouring plants in inches
• pattern: 0.866 for triangular, 1 for square

Worked Example

100 ft² planted 12 in apart on a triangular grid.

1. Area per plant = (12 ÷ 12)² × 0.866 = 0.866 ft²
2. Plants = 100 ÷ 0.866 = 115.47, rounded up to 116 plants
3. Density = 1 ÷ 0.866 = 1.15 plants per ft²

On a square grid the same bed needs 100 plants.

How to use the result

Use the count to order plugs, flats or bulbs. Ground covers and mass plantings usually use the triangular pattern because it covers the soil evenly and fills in sooner.

Limits and common mistakes

• Along the bed edges some positions fall outside the area; real counts can be a few plants lower, so round to whole flats sensibly.
• Spacing is centre to centre, between plant stems, not the gap between leaves.
• Check the recommended spacing on the plant tag; closer spacing fills faster but costs more.

Frequently Asked Questions

Why does a triangular pattern need more plants?

Each plant takes 0.866 of the area it takes on a square grid, so about 15.5% more plants fit.

How many plants per square foot at 6 inch spacing?

Square grid: 4 per ft². Triangular: 4 ÷ 0.866 = 4.62 per ft².

What is the 0.866 factor?

It is √3 ÷ 2, the height of an equilateral triangle with side 1.

Can I enter metres?

Convert first: 1 m² = 10.764 ft², 1 cm = 0.3937 in.

in a | Area to plant | ft² | 100 | 0
in s | Spacing between plants | in | 12 | 1 | 600
sel pat | Pattern | Triangular (offset rows)=0.8660254037844386, Square grid=1
out n | Plants needed | plants | ceil(round(a / ((s / 12) ^ 2 * pat), 6)) | 0
out per | Area per plant | ft² | (s / 12) ^ 2 * pat | 3
out dens | Plants per square foot | plants/ft² | 1 / per | 2