Plant Spacing Calculator
Estimate how many plants fit a bed at a chosen spacing.
Spacing is an airflow decision before it is a yield decision
The spacing on a seed packet is not about giving roots room in the abstract — it is largely about keeping foliage dry. Crowded plants hold humidity in the canopy long after rain or watering, and most of the common garden diseases (powdery mildew, downy mildew, blight, botrytis) need extended leaf wetness to establish. A bed planted 20% tighter than recommended often looks impressive in July and collapses in August.
Light is the second constraint. Once neighbouring plants shade each other's lower leaves, those leaves stop contributing and the plant sheds them, which is why an overcrowded row frequently yields less in total than a properly spaced one despite containing more plants.
Square versus offset planting
Planting on a square grid is simple to lay out but wastes space, because the diagonal gaps between four plants are larger than the spacing requires. Offsetting alternate rows into a triangular arrangement fits roughly 15% more plants at the same centre-to-centre distance, since each plant sits equidistant from six neighbours rather than four. For a bed of any size that is a meaningful difference, and it costs nothing but a slightly more careful layout.
Adjust for your conditions, not the packet
Packet spacing assumes conventional row growing with paths between rows. Intensive raised-bed methods deliberately space tighter, accepting the disease risk in exchange for shading out weeds and using the whole bed area. In humid climates, or with varieties known to be mildew-prone, go wider than the packet rather than tighter. Wind exposure matters too — a sheltered bed dries slowly and wants more space, while an exposed one dries fast and tolerates less.
Remember also that spacing is set by the mature plant. Transplants that look absurdly far apart in May are usually correct; a bed that looks well-filled at planting is almost always overcrowded.
How to use it
- Enter the bed length and width, and the spacing your variety needs.
- Compare the square and offset counts and choose your layout.
- Widen the spacing in humid climates or for disease-prone varieties.
- Judge the result against the mature plant size, not the transplant size.
Before you plant
Can I plant closer than the packet says?
Sometimes, but the trade-off is real. Tighter spacing holds humidity in the canopy and raises the risk of fungal disease, and shaded lower leaves stop producing. In humid climates go wider than the packet, not tighter.
What is the difference between square and offset spacing?
Square spacing lays plants on a simple grid; offset spacing staggers alternate rows so each plant is equidistant from six neighbours. Offset fits roughly 15% more plants in the same area at the same spacing.
Does the spacing include the path?
No. The calculation covers the planted area only. Subtract any path or access strip from your bed dimensions before entering them.
My transplants look far too far apart. Is that wrong?
Usually not. Spacing is set by the mature plant, and a bed that looks properly filled at transplanting time is almost always overcrowded by midsummer.
Disclaimer: These are general planning estimates. Seed packets, product labels, and regional frost, water, and pesticide guidance always take priority over any figure produced here. Local soil, climate, and variety differences can change the result substantially.