What this calculator does
A plant spacing calculator answers the question every gardener hits when a seed packet or nursery tag says "space 30 cm apart": how many of these will actually fit the bed. Enter the length and width of the bed and the spacing that particular plant needs, and it lays plants out in a grid and counts them.
Spacing needs vary enormously between plants, from a few centimetres for radishes to close to a metre for a mature tomato or squash plant, so this calculator never assumes a fixed number. The spacing figure is always something you type in, taken from the seed packet, plant label or your own experience with that variety.
The formula
Along the length of the bed, plants are placed edge to edge at the chosen spacing, starting from one corner: that gives floor(length ÷ spacing) + 1 plants in a row, the "+1" accounting for the plant that sits right at the starting corner. The same calculation across the width gives the number of rows. Multiplying rows by plants-per-row gives the total for a simple square grid layout.
| Term | Meaning |
|---|---|
| Spacing | The minimum distance recommended between the centres of two plants of that type, usually given on a seed packet or plant label. |
| Grid pattern | Plants placed in straight rows and columns, each spacing apart, as opposed to a denser offset or triangular layout. |
| Bed area | Length times width of the growing area, shown for reference alongside the grid-based plant count. |
The inputs explained
| Field | What to enter |
|---|---|
| Bed length (m) | The length of the garden bed or row you are planting. |
| Bed width (m) | The width of the bed. For a single row, this can be left small (close to the spacing value). |
| Spacing per plant (m) | The recommended spacing for this specific plant, taken from its seed packet or nursery label. This is not a fixed constant since it differs by plant. |
When to use it
Planning a new vegetable bed
Before buying seedlings, checking how many will actually fit a given bed at the recommended spacing avoids either wasting punnets or overcrowding plants that will end up competing for light and nutrients.
Comparing spacing options
Some crops list a range, such as "20 to 30 cm". Running both figures through the calculator shows the trade-off between a denser planting and fewer, better-spaced plants directly as a plant count.
Splitting a bed between crops
Working out how many of each plant fit a shared bed, at each plant's own spacing, helps divide the space sensibly before anything goes in the ground.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How many plants fit a 3 m by 1.5 m bed at different spacings?
The same bed, planted at a range of common spacing requirements.
| Spacing per plant | Total plants (grid pattern) | Plants per row | Number of rows |
|---|---|---|---|
| 20 cm | 128 | 16 | 8 |
| 30 cm | 66 | 11 | 6 |
| 45 cm | 28 | 7 | 4 |
How does bed size change the plant count at a fixed 30 cm spacing?
A range of bed lengths at a fixed 1.2 m width and 30 cm spacing.
| Bed length | Total plants (grid pattern) | Plants per row | Bed area |
|---|---|---|---|
| 1.5 m | 30 | 6 | 1.80 m² |
| 3 m | 55 | 11 | 3.60 m² |
| 6 m | 105 | 21 | 7.20 m² |
Questions
Why does the calculator add 1 to the row count?
A plant sits right at the starting edge of the bed as well as at each spacing interval after it, so a 3 m row at 1 m spacing fits plants at 0 m, 1 m, 2 m and 3 m, which is 4 plants from 3 intervals: floor(length ÷ spacing) + 1.
Does this account for denser offset or triangular spacing?
No, this calculates a simple square grid, which is the layout most seed packets and spacing guides assume. An offset or triangular pattern can fit somewhat more plants in the same area, but is less commonly specified for home garden beds.
What spacing should I use for my plant?
This calculator does not set a spacing for you, since it varies hugely by plant, variety and even growing conditions. Check the seed packet, plant tag or a reputable planting guide for the specific crop, and enter that figure.
Should I measure spacing from the edge of the bed or the edge of the plant?
Spacing guides normally mean the distance between plant centres, which is also how this calculator treats the length and width entered, on the assumption plants are placed starting from the bed's edge.
For a broader cubic or shape-based volume calculation elsewhere in the garden or build, see the cubic volume calculator.