How the plant spacing calculator works
The calculator lays a grid of plants over each bed and counts the points that fall inside it. It works out the grid from your spacing, your layout and whether plants sit on the edge or half a spacing in. For round and triangular beds it counts the grid points inside the shape, and for cut-outs and known areas it uses plants per square foot. The layout preview draws one possible arrangement.
Columns (half a spacing in) = floor(length ÷ spacing)
Columns (on the edge) = floor(length ÷ spacing) + 1
Triangular: row spacing = 0.866 × spacing, every other row shifted half a spacing
Density: square = 1 ÷ spacing², triangular = 1.155 ÷ spacing²
Square, rectangular and triangular layouts
In a square grid every plant has the same gap, s, to its neighbours in the row and in the next row. A rectangular layout keeps s along the row but uses a different row spacing, r, which suits crops that need wide walking aisles. A triangular layout shifts every other row by half a spacing so rows can sit closer together (0.866 × s), which fits more plants in a large bed.
Which way should the rows run?
In a triangular layout the rows of a bed can run along either side, and the count can change. Plants on the edge, rows that start and end flush with the border, and the half-spacing shift all interact with the exact length and width. The "Rows run along the" option lets you try both and keep the higher count. A square grid gives the same number either way.
Worked examples
Example 1: a 10 × 4 ft bed, 12 inch spacing, square grid
Plants sit half a spacing in from the edge. That gives 10 plants along the length and 4 along the width: 10 × 4 = 40 plants. With 10% spare you would buy 44.
Example 2: a 20 × 20 ft bed, 18 inch spacing, square or triangular
Square grid: 13 plants each way, 13 × 13 = 169 plants. Triangular grid: rows are 0.866 × 18 = 15.6 in apart, which gives 15 rows alternating 13 and 12 plants: 188 plants, about 11% more.
Example 3: a round bed 10 ft across, 12 inch spacing
The bed's area is π × 5² = 78.5 sq ft, but plants half a spacing in from the edge fit about 60 plants on a square grid. Counting on the edge instead gives 81. The difference is the plants on the rim.
Example 4: a boxwood hedge 40 ft long, 24 inch spacing, one row
One plant at each end and one every 2 ft: 40 ÷ 2 + 1 = 21 plants. With 10% spare, buy 24.
Plants per square foot at common spacings
| Spacing | Square grid | Triangular grid |
|---|---|---|
| 6 in | 4.00 | 4.62 |
| 8 in | 2.25 | 2.60 |
| 12 in | 1.00 | 1.15 |
| 18 in | 0.44 | 0.51 |
| 24 in | 0.25 | 0.29 |
| 36 in | 0.11 | 0.13 |
Multiply by your bed's area in square feet for a rough count, then use the calculator for edge rows and shapes.
Plant spacing chart
These are typical figures, not rules. Spacing varies by variety, climate and how you grow the plant, so always check the plant tag or seed packet. Pick a plant in the calculator to fill in the "calculator uses" value.
Vegetables and herbs
| Plant | Typical spacing | Calculator uses |
|---|---|---|
| Tomato (staked or caged) | 18 to 24 in (46 to 61 cm) | 24 in |
| Tomato (sprawling) | 24 to 36 in (61 to 91 cm) | 36 in |
| Pepper | 14 to 18 in (36 to 46 cm) | 18 in |
| Eggplant | 18 to 24 in (46 to 61 cm) | 24 in |
| Cucumber (trellised) | 8 to 12 in (20 to 30 cm) | 12 in |
| Zucchini / summer squash | 24 to 36 in (61 to 91 cm) | 30 in |
| Pumpkin (vining) | 36 to 72 in (91 to 183 cm) | 48 in |
| Bush beans | 3 to 4 in (8 to 10 cm) | 4 in |
| Pole beans | 4 to 6 in (10 to 15 cm) | 6 in |
| Peas | 2 to 3 in (5 to 8 cm) | 2 in |
| Lettuce (leaf) | 4 to 6 in (10 to 15 cm) | 6 in |
| Lettuce (head) | 8 to 12 in (20 to 30 cm) | 10 in |
| Spinach | 3 to 4 in (8 to 10 cm) | 4 in |
| Kale | 12 to 18 in (30 to 46 cm) | 15 in |
| Broccoli | 15 to 18 in (38 to 46 cm) | 18 in |
| Cabbage | 12 to 18 in (30 to 46 cm) | 15 in |
| Carrot | 2 to 3 in (5 to 8 cm) | 3 in |
| Beet | 3 to 4 in (8 to 10 cm) | 4 in |
| Radish | 1 to 2 in (3 to 5 cm) | 2 in |
| Onion | 3 to 4 in (8 to 10 cm) | 4 in |
| Garlic | 4 to 6 in (10 to 15 cm) | 6 in |
| Potato | 10 to 12 in (25 to 30 cm) | 12 in |
| Sweet corn | 9 to 12 in (23 to 30 cm) | 12 in |
| Strawberry | 12 to 18 in (30 to 46 cm) | 12 in |
| Basil | 10 to 12 in (25 to 30 cm) | 12 in |
Flowers and bulbs
| Plant | Typical spacing | Calculator uses |
|---|---|---|
| Marigold | 6 to 12 in (15 to 30 cm) | 8 in |
| Petunia | 12 to 18 in (30 to 46 cm) | 12 in |
| Impatiens | 8 to 12 in (20 to 30 cm) | 10 in |
| Zinnia | 6 to 12 in (15 to 30 cm) | 10 in |
| Pansy | 6 to 8 in (15 to 20 cm) | 6 in |
| Coneflower | 18 to 24 in (46 to 61 cm) | 18 in |
| Black-eyed Susan | 18 to 24 in (46 to 61 cm) | 18 in |
| Daylily | 18 to 24 in (46 to 61 cm) | 20 in |
| Hosta (medium) | 18 to 30 in (46 to 76 cm) | 24 in |
| Lavender | 18 to 36 in (46 to 91 cm) | 24 in |
| Sedum (upright) | 18 to 24 in (46 to 61 cm) | 18 in |
| Salvia | 12 to 24 in (30 to 61 cm) | 18 in |
| Tulip bulbs | 4 to 6 in (10 to 15 cm) | 5 in |
| Daffodil bulbs | 4 to 6 in (10 to 15 cm) | 6 in |
Shrubs and hedges
| Plant | Typical spacing | Calculator uses |
|---|---|---|
| Boxwood | 18 to 36 in (46 to 91 cm) | 24 in |
| Arborvitae (hedge) | 24 to 48 in (61 to 122 cm) | 36 in |
| Holly (hedge) | 36 to 60 in (91 to 152 cm) | 48 in |
| Hydrangea | 36 to 72 in (91 to 183 cm) | 48 in |
| Shrub rose | 36 to 48 in (91 to 122 cm) | 36 in |
| Privet (hedge) | 18 to 36 in (46 to 91 cm) | 24 in |
Groundcovers
| Plant | Typical spacing | Calculator uses |
|---|---|---|
| Creeping thyme | 6 to 12 in (15 to 30 cm) | 8 in |
| Vinca (periwinkle) | 12 to 18 in (30 to 46 cm) | 12 in |
| Pachysandra | 6 to 12 in (15 to 30 cm) | 8 in |
| Ajuga | 6 to 12 in (15 to 30 cm) | 10 in |
| Liriope | 12 to 18 in (30 to 46 cm) | 12 in |
Mistakes to avoid
- Using the mature width as a rule. Plant tags give a typical spacing for a purpose. Tight spacing can be right for a quick-fill border and wrong for a specimen shrub.
- Forgetting the edge. Plants right on the border spill over. Half a spacing in is a safe default.
- Mixing up inches and feet. Spacing is entered in inches (or cm), bed sizes in the units you pick. The calculator converts both.
- Dividing area by spacing instead of spacing squared. A 40 sq ft bed at 12 in is 40 plants, not 40 ÷ 12.
- Ignoring the shape. Round and triangular beds hold fewer plants than their area suggests because of the edge. Use the shape options.
Plants per 100 square feet and per acre
Use this for a quick estimate before you enter your real bed. It ignores edge rows, so the calculator above is more exact for small beds.
| Spacing | Plants per 100 sq ft (square) | Plants per 100 sq ft (triangular) | Plants per acre (square) | Plants per acre (triangular) |
|---|---|---|---|---|
| 6 in | 400 | 462 | 174,240 | 201,195 |
| 8 in | 225 | 260 | 98,010 | 113,172 |
| 12 in | 100 | 115 | 43,560 | 50,299 |
| 18 in | 44 | 51 | 19,360 | 22,355 |
| 24 in | 25 | 29 | 10,890 | 12,575 |
| 36 in | 11 | 13 | 4,840 | 5,589 |
Per hectare, multiply the per acre figure by 2.47. Per square metre, multiply plants per square foot by 10.76.
Frequently asked questions
How do I calculate how many plants fit in a bed?
Divide the bed area by the area each plant needs. With spacing in feet, plants = area ÷ spacing². With spacing in inches, plants per square foot = 144 ÷ spacing². For example, 12 inch spacing gives 1 plant per square foot. The calculator also counts the real grid, including edges and partial rows.
What is the difference between square and triangular spacing?
Square spacing puts plants in straight rows and columns. Triangular spacing offsets every other row, so each plant is the same distance from its neighbors. It fits about 15% more plants into a large area at the same spacing, and it looks fuller. In small beds the difference can be smaller because of the edge rows.
Should I plant right at the edge of the bed?
Usually not. Plants at the very edge can spill onto paths or lawn, so many people keep them about half a spacing in. The calculator's default is half a spacing in from the edge, and you can switch to plants on the edge.
How far apart should I plant a hedge?
It depends on the plant and how fast you want it to fill. Typical figures are 18 to 36 inches for boxwood, 24 to 48 inches for arborvitae and 36 to 60 inches for holly. Closer spacing fills in sooner but costs more plants. Use the hedge option and check your plant tag.
How many spare plants should I buy?
About 5 to 10% extra covers losses and replacements. You can set the spare percentage in the calculator and it will round up to whole plants.
What if the plant tag gives a range of spacing?
Spacing at the lower end of the range fills the bed faster, while the upper end gives plants room to reach full size and can reduce crowding and disease. Pick based on how quickly you want coverage and how long you will leave the bed before dividing or thinning.
What is the 3-5-7 rule in landscaping?
It is a design guideline: plant in odd-numbered groups of 3, 5 or 7 rather than in pairs or evenly spaced rows, because odd groups look more natural. It is about looks, not growth, so keep the spacing between plants in each group at what the plant needs.
What is the formula for plant spacing?
For a square grid, plants = area ÷ (spacing × spacing). For a triangular grid, plants = area ÷ (spacing × 0.866 × spacing). Use the same unit for both. At 12 inch spacing that is 1 plant per square foot, and per acre it is 43,560 ÷ spacing in feet squared.
How many plants can I grow in 100 square feet?
At 12 inch spacing, 100 square feet holds about 100 plants in a square grid and about 115 in a triangular grid. At 18 inches it is about 44 and 51, at 24 inches about 25 and 29, and at 6 inches about 400 and 462. Edge rows change small beds.
How far apart should ground cover be planted?
Most ground covers go 6 to 18 inches apart. Closer spacing, such as 6 to 12 inches for creeping thyme, ajuga or pachysandra, fills in faster but costs more. Wider spacing, such as 12 to 18 inches for vinca or liriope, is cheaper and fills in over a few seasons. Check the plant tag.
Can I plant tomatoes 12 inches apart?
It is usually too close. Staked or caged tomatoes are commonly spaced 18 to 24 inches, and sprawling types 24 to 36 inches. Compact or dwarf varieties that you prune and stake can go closer, but you trade airflow and sunlight for more plants.
What happens if you plant tomatoes too close together?
The plants shade and crowd each other, air moves less and leaves stay wet longer, which raises the risk of leaf diseases. Yields per plant and fruit size often drop, and picking and pruning get harder.
What should not be planted next to tomatoes?
Gardeners commonly avoid planting fennel and members of the cabbage family such as broccoli and cabbage close to tomatoes, and they keep potatoes away because both share blight. Corn can share tomato fruitworm. Companion advice varies, so treat it as a guide.
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