Plant Spacing Calculator
Find how many plants you need for a flower bed, a vegetable garden, or ground cover. Enter the size of each bed and the spacing on the plant tag, and choose a grid or triangular layout. Add the plants per tray to see how many trays to buy.
Add more beds, or subtract areas inside a bed that need no plants, such as a path or a tree.
- Choose US or Metric. You can still change the unit of any single field.
- Pick the shape of each bed and enter its dimensions. Use Add section for more beds. Set a section to Subtract for parts of a bed you won't plant, such as a path through the bed, stepping stones, or the base of a tree. For a ring of plants around a tree, choose the ring shape.
- Enter the Plant spacing from the plant tag. It's the distance from the center of one plant to the center of the next. If the tag gives a range, such as 18 to 24 in, the narrow end gives more plants and a fuller look sooner, and the wide end gives fewer.
- Leave Row spacing blank unless your rows are farther apart than the plants in a row, as in many vegetable beds.
- Choose the Layout. Grid lines the plants up in rows and columns. Triangular staggers the rows, which is the usual way to plant ground cover and mass plantings.
- Optionally, enter the Plants per tray to see how many trays to buy, and a price per plant or per tray to estimate the cost.
Dimension fields accept whole numbers, decimals, fractions, and mixed
numbers, such as 12, 10.5, 3/4, or
6 1/2. On a slope, measure the bed along the ground, since
the plants are spaced along the ground.
How many plants you need
Each plant takes up a patch of the bed that is one plant spacing long and one row spacing wide. The calculator divides the area of the bed by the area of that patch:
Plants = area ÷ (plant spacing × row spacing), rounded up
Row spacing for a triangular layout = plant spacing × 0.866
Trays = plants ÷ plants per tray, rounded up
If you leave the row spacing blank, a grid uses the plant spacing for the rows too. Convert both spacings and the area to the same unit before you divide. For example, 12 in is 1 ft, so plants 12 in apart take up 1 ft² each, and a 100 ft² bed needs 100 plants. The density shown with the result is 1 ÷ (plant spacing × row spacing), the number of plants per square foot or square meter.
With several beds, the calculator adds the sections set to Add, subtracts those set to Subtract, and rounds up once for the total. To see the count for each bed on its own, calculate each bed separately. For shapes other than rectangles, it uses these formulas:
| Shape | Area |
|---|---|
| Rectangle | length × width |
| Circle | π × diameter² ÷ 4 (or π × radius²) |
| Triangle (base and height) | base × height ÷ 2 |
| Triangle (three sides) | Heron's formula: √(s(s − a)(s − b)(s − c)), where s = (a + b + c) ÷ 2 |
| Trapezoid | (parallel side A + parallel side B) ÷ 2 × height |
| Ring | π × (outer diameter² − inner diameter²) ÷ 4 |
| Rectangular border | outer length × outer width − (outer length − 2 × border width) × (outer width − 2 × border width) |
| Known area | the area you enter |
Grid or triangular layout
- Grid: Rows and columns lined up, for square or rectangular spacing.
- Triangular: Rows offset by half a space, so the plants are staggered.
In a triangular layout with the row spacing left blank, each row is shifted by half a space and the rows are 0.866 × the plant spacing apart, so every plant is the same distance from its six neighbors. The rows sit closer together, so you need about 15% more plants than a grid with the same spacing. New Mexico State University's guide to designing a pecan orchard gives the same figure for trees: about 15% more trees per acre.
University of Illinois Extension recommends planting ground covers in a staggered or diamond pattern for best results, and the City of Bellevue, Washington, plants ground cover at equal triangular spacing in its parks. Use the triangular layout for ground cover and mass plantings, and the grid for rows, such as a vegetable bed. Extension and nursery charts of plants per area use a grid, so the grid result matches them.
If you enter a row spacing, the calculator uses it for either layout. Staggering the rows doesn't change the area each plant takes up, so a triangular layout with the row spacing equal to the plant spacing gives the same count as a grid. For plants the same distance apart in every direction, leave the row spacing blank.
Spacing at the edges of a bed
The count is a number to buy that won't fall short when you set the outer plants at least half a spacing in from the edges of the bed. For example, a bed 10 ft × 10 ft planted 12 in apart in a grid holds 10 rows of 10 plants, 6 in from the edges, which is exactly the 100 the calculator shows.
When the spacing doesn't divide the bed evenly, the count is a little more than you can fit. The same bed planted 18 in apart needs 45 plants by area, the number University of Illinois Extension's chart gives for 100 ft². Starting half a spacing in from the edges, 6 rows of 6 fit, or 36 plants. A triangular layout also leaves gaps at the ends of the shifted rows, so it can fit slightly fewer than the count. Planting right on the edges fits more: 11 rows of 11, or 121 plants, at 12 in.
The City of Bellevue sets ground cover half a spacing from curbs and paving. To leave a wider gap along the edges, enter the bed a little smaller by that gap.
Narrow strips and single rows
In a strip less than twice the plant spacing wide, the plants go in a single row, and the area doesn't match the count. Count the row instead: divide the length by the spacing and round down to start half a spacing from each end, or add 1 to plant at both ends. A border 10 ft long with plants 18 in apart takes 6 plants, or 7 with a plant at each end. The same goes for a hedge. The nursery Lurvey's planting sheet counts hedge plants by the linear foot and adds 1.
Where to find the plant spacing
Use the spacing on the plant tag, the seed packet, or the nursery's listing. The perennial grower Plants to Grow describes spacing as on center, the distance between the centers of the plants, and spaces annuals 6 to 12 in or more apart and perennials about 12 to 30 in or more. Metric sources, such as the UK's Royal Horticultural Society, give spacing in centimeters, such as 60 cm for Cotoneaster horizontalis. For wide spacing, you can choose ft or m as the unit.
Vegetables are often spaced one way within a row and another between rows. University of California Cooperative Extension's planting guide for Napa County, for example, spaces cabbage 24 in apart in the row with rows 36 in apart. Enter the first as the plant spacing and the second as the row spacing.
For bulbs, enter the spacing on the bag. Some plants, such as wildflower plugs, are sold by density instead, such as 5 plants per square meter. Multiply the total area in the result by that density to get the number of plants.
How many plants come in a tray
Bedding plants and ground cover are often sold in flats, trays, or packs. The number per tray depends on the product. Some examples:
| Source | Plants per tray |
|---|---|
| Sunset's ground cover chart (US) | 48, 64, 72, or 100 per flat |
| Lurvey's planting sheet (US) | 48-cell flats of annuals |
| Habitat Aid wildflower plugs (UK) | 104 per tray |
These are only examples. Check the number on the product you buy, and enter it as the Plants per tray.
Examples
A square flower bed
A bed 10 ft × 10 ft is 100 ft². With plants 12 in apart in a grid, each plant takes up 1 ft², so you need 100 plants. In a triangular layout, the rows are 12 × 0.866 = 10 3/8 in apart, each plant takes up 0.866 ft², and 100 ÷ 0.866 = 115.47, so you need 116 plants. With 18 plants per tray, buy 7 trays.
Ground cover around a tree
A bed 12 ft × 6 ft and a round bed 8 ft across, with a 2 ft circle left bare at the base of a tree, add up to 72 + 16π − π = 72 + 15π = 119.12 ft². Enter the tree as a third section set to Subtract. Planted 18 in apart, each plant takes up 2.25 ft², so you need 53 plants in a grid, or 62 in a triangular layout.
Vegetable rows
A bed 20 ft × 9 ft is 180 ft². With plants 24 in apart and rows 36 in apart, each plant takes up 2 × 3 = 6 ft², so you need 30 plants: 3 rows of 10, starting 1 1/2 ft from the long edges and 1 ft from the ends.
Metric dimensions
An area of 50 m² planted 45 cm apart in a triangular layout has rows 389.7 mm apart, so each plant takes up 0.45 × 0.3897 = 0.1754 m², and you need 286 plants. In trays of 104 plug plants, buy 3 trays.
FAQ
About 100 plants spaced 12 in apart in a grid, or 116 in a triangular layout. The bed is 100 ft², and each plant takes up 1 ft² in a grid or 0.866 ft² in a triangular layout, so 100 ÷ 0.866 = 115.47, rounded up to 116.
It depends on the spacing. In a grid, you need 4 plants per square foot at 6 in apart, 1.78 at 9 in, 1 at 12 in, 0.44 at 18 in, and 0.25 at 24 in. A triangular layout needs about 1.15 times as many.
It's the distance from the center of one plant to the center of the next, not the gap between their leaves. A tag that says 12 in on center means the stems are 12 in apart.
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