Seed Spacing Calculator

Seed spacing determines how many plants fit in a given garden area and how healthy they grow. Crowded plants compete for light, water, and nutrients, resulting in poor yields, disease, and weak growth. Properly spaced plants produce stronger stems, better airflow, and higher yields per plant.

Formulas: Plants per Row = Row Length ÷ Spacing Between Plants (rounded down) Total Plants = Plants per Row × Number of Rows Bed Width = Number of Rows × Row Spacing Square-foot gardening: Plants per Sq Ft = 144 ÷ (Recommended Spacing in inches)²

Note the absence of a “+1” on the first line. Counting both ends of the row, the way you would count fence posts, is the commonest error in spacing arithmetic and it inflates a long row by one plant and a short one by a third. A plant needs half its spacing of clear ground on each side, so the first and last plants sit half a spacing in from the ends rather than on them.

Note too that the row length and the spacing are in different units: rows in feet or metres, spacing in inches or centimetres. The unit selector above tells the calculator which system you are using. It is worth saying explicitly because this page used to infer it by comparing the two numbers, and any row longer than its spacing figure came out roughly twelve times too short.

Standard spacing chart (recommended in-row spacing):

Worked example, raised bed planning: A 4-foot wide by 8-foot long raised bed, growing bush beans. Bean spacing: 4 inches in the row, rows 21 inches apart.

Row length is 8 ft = 96 inches Plants per row = 96 ÷ 4 = 24 plants per row The bed is 4 ft = 48 inches wide, so at 21-inch rows it takes 2 rows Total = 24 × 2 = 48 plants Seeds to buy, adding 15% for the ones that never come up: 56

Most bean packets hold 100 or more, so one packet does it with plenty left for a second sowing three weeks later.

Succession planting: sowing the whole row at once gives you forty pounds of beans in the same fortnight and none either side of it. Sow a third of the row every two to three weeks and the harvest spreads over six to eight. This is the single change that does most for a small vegetable garden, and it costs nothing.

Thinning: most seed is sown closer than the final spacing and then thinned once the seedlings are up, which is the only honest way to deal with germination that is never 100%. Snip the extras off at soil level rather than pulling them, so the roots of the ones you are keeping stay put. Thinning always feels wasteful and is always right; a row left unthinned yields less than half what a thinned one does.