GardenCalcs.uk
Companion Planting Layout Calculator
Calculate companion planting layout and spacing for common vegetable combos.
The lead vegetable; companions and spacing are looked up from RHS grow-your-own figures for this crop.
The long side of the bed, along which plants sit in each row. A standard raised bed is 2.4–3 m.
The short side, across which rows run. Keep to 1.2 m so the centre is reachable from both sides without treading on soil.
Centre-to-centre gap between rows across the bed. 30 cm suits salad/roots; allow 45–60 cm for brassicas, beans and courgettes that sprawl.
Unplanted margin kept clear at every bed edge for access and airflow; it is subtracted from both length and width. 15 cm is typical.
How We Calculate This
Select your main crop and enter your bed dimensions. The calculator looks up recommended companions and crops to avoid, then estimates plant counts from each species' optimal spacing.
Rows run across the bed width at the row spacing (pitch) you set; plants per row are spaced along the bed length at the crop's own spacing (both use the fencepost rule: plants = length ÷ spacing + 1). Companions are counted as interplanted accents — set between the main plants and at row ends — so they stay roughly equal to or fewer than the main crop rather than forming a second full crop. An edge buffer keeps plants away from the bed edges for access and airflow.
Frequently Asked Questions
Many combinations are well-documented: alliums deter carrot fly, marigolds repel nematodes, and the Three Sisters (corn, beans, squash) is a proven system used for centuries. At worst it increases biodiversity.
Close enough to benefit each other but not competing for light, water or nutrients. Generally 15-30 cm between different species, following each crop recommended spacing.
An ancient method: sweetcorn provides support for climbing beans, beans fix nitrogen in the soil, and squash shades the ground reducing weeds. Plant in blocks rather than rows for best results.
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Last updated: March 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.