Understanding your result
Planting positions equal rows multiplied by plants per row. The span is measured between the first and last plant centres; it does not include plant width or the surrounding margin.
To estimate the fill beneath this layout, use the Raised Bed Soil Calculator with the bed’s inside dimensions.
The formula
The usable centre span is the bed dimension after both edge margins are removed. Each complete spacing interval connects two positions, so one is added after rounding down. Any unused remainder can be distributed between the two edges to centre the grid.
Worked example
A 300 cm by 120 cm bed with 15 cm clearance at every edge has usable centre spans of 270 cm and 90 cm. At 30 cm spacing both ways, it fits ten plants per row and four rows, giving forty positions.
How to use this calculator
- Measure the usable rectangular bed in centimetres.
- Enter centre-to-centre plant spacing and the distance between rows.
- Set a minimum margin from each edge to the first plant centre.
Spacing is a planting decision
Use spacing appropriate to the crop or plant variety and its intended mature size. This calculator counts positions after that decision; it does not determine a horticulturally suitable distance. Separate row spacing can reserve room for access or accommodate crops whose recommended row and within-row distances differ.
Why area divided by spacing can differ
An area-density calculation ignores boundaries. A narrow bed can have substantial area but still accommodate only one row at the requested clearance. This layout method respects each side separately. It assumes aligned rows, and it excludes staggered triangular patterns, paths inside the rectangle, circular beds, and mixed planting arrangements.
Assumptions & limitations
What this calculation assumes
- All centres use an aligned rectangular grid.
- The same minimum edge clearance applies on all four sides.
What to keep in mind
- Counts planting locations, not germination, survival, or harvest yield.
Common questions
Why is there one extra position after dividing?
Spacing counts gaps. Three gaps connect four plant centres, which is why the formula adds one.
What happens if only one centre fits?
A single position has zero centre-to-centre span. It can be centred within the bed while respecting the edge clearance.