A spacing figure usually describes the distance between plant centres. It does not mean that a plant can sit anywhere inside a square of that size without affecting its neighbours. A small bed needs a clear row direction and a decision about the first plant's distance from each edge.
The Plant Spacing Calculator counts a rectangular grid after removing the entered centre setback from both ends of each dimension. It also checks the same spacings rotated through 90 degrees. The two results can differ, particularly in a long, narrow bed.
What fits in a three metre bed?
Use a bed 3 m long and 1.2 m wide. Set plant spacing along the row to 30 cm, spacing between rows to 40 cm and the centre setback on every edge to 15 cm.
After subtracting both setbacks, the usable centre span is 2.7 m along the bed and 0.9 m across it. Ten centres fit along a row and three rows fit across the width, making 30 plants. The tool includes both endpoints where the spacing fits exactly.
Rotate the same pair of spacings and the count becomes seven centres along the length and four rows across the width, or 28 plants. That comparison does not say the smaller count is horticulturally worse. It simply shows how the entered rectangular geometry changes.
Keep the setback and spacing distinct
The setback locates the first and last allowable centres relative to the boundary. Row spacing locates one row relative to the next. Increasing a setback can remove a complete row even when the nominal bed area changes very little.
If the setbacks leave no usable centre span, the count becomes zero. A span of exactly zero can hold one centre along that dimension. This is why an endpoint counting method differs from dividing bed area by a notional area per plant and rounding the result.
The diagram is a preview of the count
Large layouts display only a capped number of plant markers. The reported count and orientation table remain the full calculation. Do not count the visible circles to infer a large order; use the numerical results.
The model uses aligned rectangular rows. It does not optimise triangular planting, mixed crops, access paths, trellised spread or companion planting. Crop spacing remains an input from your chosen variety and growing arrangement.
After choosing the final plant target, Seed Quantity Calculator can account for expected germination and establishment. Use Garden Bed Layout Planner first if the garden still needs its beds and walking paths allocated before the individual planting grids make sense.