How many plants do I need?
Type the size of the bed and the spacing on the plant tag, and pick a square or staggered pattern. The plant spacing calculator tells you how many plants to buy, with a few extra for edges and losses.
- Plants to buy
- 105
Buy 105 plants (100 to fill the bed, plus extra).
- Plants without extra
- 100
- Area per plant (ft²)
- 1
- Area per plant (m²)
- 0.0929
- Row spacing (in)
- 12
Plants to buy: 105. Buy 105 plants (100 to fill the bed, plus extra).
How to calculate
Counts the plants that fill a bed at a given spacing, on a square grid or a staggered triangular grid, with an extra share for edges and losses.
Example with the default inputs (Bed known by Length and width, Bed length 10 ft, Bed width 10 ft, Plant spacing 12 in, Pattern Square grid, Extra plants 5%): Buy 105 plants (100 to fill the bed, plus extra).
Method: Plants = ⌈bed area ÷ area per plant × (1 + extra)⌉, with area per plant = spacing² (square grid) or spacing² × √3 ÷ 2 ≈ 0.866 × spacing² (triangular grid).
- The count fills the area at the spacing; it does not place plants along the edges. Narrow or oddly shaped beds may take a few more or fewer.
- The 5% default extra follows the nurseries’ advice of 5 to 10% for edges, corners and losses.
Worked examples
Each example is checked against the calculator on every build.
- Bed known by Length and width, Bed length 10 ft, Bed width 10 ft, Plant spacing 12 in, Pattern Square grid, Extra plants 0% gives Plants to buy 100, Plants without extra 100, Area per plant (ft²) 1, Row spacing (in) 12.Source: University of Missouri Extension, G6835 Ground Covers (Table 1: 100 plants cover 100 ft² at 12 in and 225 ft² at 18 in), https://extension.missouri.edu/publications/g6835; Bloomin Designs Nursery, Plant Calculator (square: area ÷ (spacing × spacing); triangular rows 0.866 × spacing apart; order 5–10% extra), https://www.bloomindesigns.com/plant-calculator/
- Bed known by Area, Bed area 225 ft², Plant spacing 18 in, Pattern Square grid, Extra plants 5% gives Plants without extra 100, Plants to buy 105, Area per plant (ft²) 2.25.Source: University of Missouri Extension, G6835 Ground Covers (Table 1: 100 plants cover 100 ft² at 12 in and 225 ft² at 18 in), https://extension.missouri.edu/publications/g6835; Plant Addicts, Free Plant Spacing Calculator (triangular row spacing = 0.866 × spacing; add 5% extra), https://plantaddicts.com/free-plant-spacing-calculator/ (5% extra)
- Bed known by Area, Bed area 100 ft², Plant spacing 12 in, Pattern Triangular (staggered), Extra plants 0% gives Plants without extra 116, Area per plant (ft²) 0.866025, Row spacing (in) 10.392305.Source: Bloomin Designs Nursery, Plant Calculator (square: area ÷ (spacing × spacing); triangular rows 0.866 × spacing apart; order 5–10% extra), https://www.bloomindesigns.com/plant-calculator/ (rows 0.866 × spacing apart; about 15% more plants)
- Bed known by Length and width, Bed length 9.843 ft, Bed width 3.937 ft, Plant spacing 11.81 in, Pattern Square grid, Extra plants 10% gives Plants without extra 40, Plants to buy 44, Area per plant (m²) 0.09.Source: Bloomin Designs Nursery, Plant Calculator (square: area ÷ (spacing × spacing); triangular rows 0.866 × spacing apart; order 5–10% extra), https://www.bloomindesigns.com/plant-calculator/
How it works
- Bed area A: length × width, or the area you type.
- Area per plant: on a square grid, s × s for spacing s. On a triangular (staggered) grid, the rows are s × √3 ÷ 2 ≈ 0.866 s apart and the plants s apart along each row, so each plant takes s² × √3 ÷ 2 ≈ 0.866 s².
- Plants without extra = ⌈A ÷ area per plant⌉.
- Plants to buy = ⌈A ÷ area per plant × (1 + extra ÷ 100)⌉.
- Row spacing = s (square) or 0.866 s (triangular), shown in inches.
Rules. Bed sides from 1 cm to 10 km; area from 0.01 m² to 10,000,000 m²; spacing from 1 cm to 30 m; extra from 0% to 100%.
Exact arithmetic. Lengths and areas are read as the exact decimals you typed in their units (1 ft = 0.3048 m, 1 in = 0.0254 m), so a square-grid count is exact and a whole number of plants is not rounded up by mistake. The triangular grid uses √3, so its count is a double-precision float before rounding up.
Output format. Plant counts are whole numbers, rounded up. Area per plant shows 3 decimals in ft² and 4 in m²; row spacing 2 decimals in inches, rounded half up.
Assumptions
- The count fills the area at the spacing and does not fit plants to the bed’s edges.
- The default 5% extra follows the nurseries’ 5 to 10% advice.
Worked examples by hand
10 × 10 ft bed at 12 in, square, no extra (Missouri Table 1). A = 100 ft²; each plant 1 ft²; 100 plants. Rows 12 in apart.
225 ft² at 18 in, square, 5% extra (Missouri Table 1). Each plant 1.5 × 1.5 = 2.25 ft²; 225 ÷ 2.25 = 100; × 1.05 = 105 plants.
100 ft² at 12 in, triangular, no extra. Each plant 1 × 0.8660 = 0.866 ft²; 100 ÷ 0.8660 = 115.47, rounded up 116. Rows 12 × 0.8660 = 10.39 in apart.
3 × 1.2 m bed at 30 cm, square, 10% extra. A = 3.6 m²; each plant 0.3 × 0.3 = 0.09 m²; 3.6 ÷ 0.09 = 40; × 1.1 = 44 plants.
Other questions people ask
How many plants do I need for my bed?
Divide the bed area by the area each plant takes. At 12 in spacing on a square grid each plant takes 1 ft², so a 10 × 10 ft bed takes 100 plants, or 105 with 5% extra.
What is triangular spacing?
Every other row is shifted by half a space, so each plant sits at the corner of equal triangles. The rows are 0.866 × the spacing apart, which fits about 15% more plants: 116 instead of 100 in 100 ft² at 12 in.
Square or triangular, which is better?
A staggered (triangular) pattern covers the ground faster and looks more natural, so it is the usual choice for ground covers and hedges. A square grid is easier to lay out in rows.
How much extra should I buy?
Nurseries suggest 5 to 10% extra for curved edges, corners and plants that fail. The page adds 5% unless you change it.
What spacing should I use?
Use the spacing on the plant tag, which is about the plant’s width when grown. Missouri Extension’s table shows how fast it adds up: 100 plants cover 25 ft² at 6 in, 100 ft² at 12 in and 225 ft² at 18 in.
My bed is not a rectangle. What do I do?
Measure or estimate its area and choose Area. For a round bed, area = 3.1416 × radius²; for an L-shaped bed, split it into rectangles and add their areas.