Plant spacing calculator

How many plants do I need?

Divide the bed area by the space each plant takes. In a square grid each plant takes spacing × spacing: a 10 × 10 ft bed at 12-inch spacing holds 100 plants.

What is triangular (staggered) spacing?

Rows offset by half a space so the plants form equilateral triangles. Each plant then takes spacing² × 0.866, so the same bed fits about 15% more — 115 plants at 12 inches.

Where does 0.866 come from?

It is √3 ÷ 2, from the geometry of equilateral triangles. The Washington State DOT’s roadside manual uses it — 3-foot spacing gives one plant per 7.8 sq ft — and NMSU Extension notes about 15% more trees per acre in a triangle layout.

Which spacing should I use?

The spacing on the plant tag or seed packet. The calculator turns it into a count.

Does it account for edges?

No — it divides area by area. Leave room at the edges and paths, and round to fit your actual rows.

What if the rows and the plants in a row are spaced differently?

The calculator uses one spacing in both directions, so convert. The area each plant needs is the in-row distance times the row distance, and entering the square root of that product in square mode gives the same count. Colorado State University Extension lists beans at 12 inches between rows and 4 inches between plants: 4 × 12 = 48 square inches, whose square root is 6.9 inches. In a 4 × 8 ft bed that is 96 plants.

How many plants fit in an acre?

An acre is 43,560 square feet. At 3-foot spacing a square grid takes 9 square feet per plant, so 4,840 plants. A triangular pattern takes 7.794 square feet each, so 5,588. The Washington State DOT roadside manual adds two more plants to its triangular formula.

How the count is found

Each plant is given its own patch of ground and the bed area is divided by it. In a square grid the patch is spacing × spacing. In the staggered pattern every plant is the same distance from its six neighbors, so the plants sit at the corners of equilateral triangles; the rows are then 0.866 times the spacing apart, the patch is spacing² × 0.866, and the bed holds 15.5% more. The answer is a whole number rounded down, and it assumes the bed is one open rectangle with nothing lost at its edges.

Worked example

A 4 × 8 ft raised bed is 32 square feet. Colorado State University Extension gives peppers as 15 by 15 inches, three across a 4 ft bed. The square formula gives 20 plants and the staggered formula 23. Laying out whole 15-inch squares gives 3 across and 6 along, 18 plants: the formula counts the fractions of squares left at the edges. The Washington State DOT manual makes the same point about its formula, that large areas can come up a little short around the edges. Treat the result as an order quantity and then fit it to the real rows.

Common mistakes

Entering the final spacing from the plant tag for a crop that is grown in rows with a different distance between them gives the wrong area, as the bean example shows. The staggered pattern is harder to lay out: New Mexico State's orchard guide calls the triangle layout difficult and seldom used there, even though it fits about 15% more trees. Finally, spacing is measured center to center (the WSDOT manual calls it on-center), not as the gap between plants.

Sources: Washington State Department of Transportation, Roadside Manual M 25-30.04 (October 2017), Appendix D, Plant Spacing; E. Herrera, “Designing a Pecan Orchard,” Guide H-607, New Mexico State University Cooperative Extension Service; Colorado State University Extension, “Block Style Layout in Raised Bed Vegetable Gardens” (GardenNotes 713). Related: raised bed soil calculator, mulch calculator, compost calculator, fence calculator. How we check our calculators.