What this calculator works out
This calculator divides a bed area by the space each plant occupies — row spacing multiplied by in-row spacing — to give the number of plants it will hold.
The result is a grid capacity. Real beds have edges and paths, so treat it as an upper figure rather than a target.
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Before you plan a bed
- Take spacings from the seed packet for the specific variety. They vary widely — onions at 10 cm, brassicas at 45 to 60 cm.
- Row spacing is the gap between rows; plant spacing is the gap within a row. Many crops use different figures for each.
- Deduct any path or access strip from the bed area before entering it.
- The calculation rounds down, because a partial plant space holds nothing.
Traditional row spacing leaves walking room between rows, which suits large plots worked with a hoe. Bed systems worked from the edges use equidistant spacing in both directions, which fits noticeably more plants into the same area — the whole argument for raised beds and square-foot gardening.
How this calculator works
Area divided by the space per plant:
Space per plant = (row spacing ÷ 100) × (plant spacing ÷ 100)
Plants = bed area ÷ space per plant, rounded downDividing by 100 converts centimetres to metres so the units match the bed area. The result assumes plants fill the area on a regular grid with no allowance for edges — in practice a metre-wide bed loses proportionally more to edge effects than a wide one.
Worked example: a 6 m² bed
Using the default figures — 6 m² with rows 45 cm apart and plants 30 cm apart:
- Space per plant: 0.45 × 0.30 = 0.135 m²
- Plants: 6 ÷ 0.135 = 44.4, rounded down to 44
Now try equidistant spacing at 35 cm in both directions, which is a common bed-system approach for a crop of this size. Space per plant becomes 0.1225 m² and the bed holds 48 — four more plants from the same area, with no plant closer to its neighbour than 35 cm. That is the practical case for bed systems in one calculation.
Common mistakes
- Using a generic spacing. Packet figures vary enormously between crops and varieties.
- Including paths in the bed area. Measure the growing area only.
- Planting to the theoretical maximum. Crowded plants compete for light, water and nutrients.
- Ignoring succession. A bed cropped twice a season needs planning as two plantings.
- Forgetting mature size. Spacing is set by the plant at harvest, not at planting.
Frequently asked questions
Can I plant closer than the packet says?
Sometimes, with consequences. Closer spacing produces more but smaller plants, which suits salad leaves, beetroot and carrots where small is acceptable. For crops where size matters — cauliflower, sweetcorn, squash — close spacing reduces yield rather than increasing it, and increases disease risk by reducing airflow.
What is square-foot gardening?
A bed system dividing the growing area into 30 cm squares, each planted with a set number of a given crop — one cabbage, four lettuces, sixteen radishes. It is a practical way of applying equidistant spacing without calculating, and it suits small raised beds worked from the edges.
How do I plan for succession?
Work out what the bed holds, then plan two or three sowings a few weeks apart rather than one large sowing. For fast crops such as lettuce and radish this doubles or triples the useful output from the same area, and avoids a glut followed by nothing.
Does spacing affect watering?
Yes, in both directions. Densely planted beds shade the soil and lose less to evaporation, but the plants collectively draw more water. Widely spaced plants on bare soil lose more to evaporation. Mulching between plants addresses the second problem without creating the first.
Is what I enter stored?
No. Measurements are processed in your browser and never transmitted or retained.
Related tools
References
- Royal Horticultural Society — vegetable growing guides, spacing and succession sowing
- GOV.UK — guidance on growing food and allotment provision
Sources are checked at publication and can change — how I choose and check references.