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Plant Spacing Calculator

Work out how many plants fit a bed at a given spacing, compare square and offset layouts, and see the 15% more that staggering the rows buys you.

How to use this calculator

  1. 1Measure the bed rather than the plot. Paths and edging are not planting area.
  2. 2Use the in-row spacing from the seed packet or plant label — it is the number that describes what the mature plant needs.
  3. 3Decide whether anyone needs to walk between the rows. In a bed reached from the side, nobody does, and the row spacing can collapse to the in-row figure.
  4. 4Try the offset layout. It fits 15.5% more plants at exactly the same neighbour spacing, and the only cost is setting out alternate rows half a space over.
  5. 5Space for the mature plant, not the seedling. Everything looks far too far apart on planting day, and crowding costs yield, airflow and disease resistance.
  6. 6Keep beds to four feet wide where they are reached from both sides, and two feet against a wall.

How the calculation works

Usable length = bed length − 2 × margin (same for width) Plants per row = floor(usable length ÷ in-row spacing) + 1 Square grid: rows = floor(usable width ÷ row spacing) + 1 total = rows × plants per row Triangular grid: row spacing = in-row spacing × √3⁄2 ≈ 0.866 × spacing alternate rows hold one fewer plant area per plant = spacing² × 0.866, so density rises 15.5%
In-row spacing
Distance between plants along a row. Usually the single number on a seed packet
Row spacing
Distance between rows. Normally wider, because rows exist for a person to walk down
√3⁄2
The row-spacing factor for an equilateral triangular grid — about 0.866. Where the 15.5% density gain comes from
Margin
How far in from the bed edge the first plant sits. Half the in-row spacing is a reasonable default

Plants sit at both ends of a row, which is why the count is a floor division plus one rather than a straight division.

In a triangular layout the offset rows start half a space in, so they hold one fewer plant than the aligned rows.

The 15.5% figure is the theoretical density gain. Fitting a real grid into a real bed lands slightly either side of it, because beds are rarely exact multiples of the spacing.

Worked example

A 20 × 4 ft bed at 12 in spacing in a square grid

  1. 1.The bed is 240 in by 48 in. A 6 in margin on each side leaves 228 in of usable length and 36 in of usable width.
  2. 2.Plants per row = floor(228 ÷ 12) + 1 = 19 + 1 = 20.
  3. 3.Rows at 18 in = floor(36 ÷ 18) + 1 = 2 + 1 = 3.
  4. 4.Total = 3 × 20 = 60 plants, which is 0.75 per square foot across the 80 sq ft bed.
  5. 5.Switching to an offset layout closes the rows to 12 × 0.866 = 10.4 in, giving floor(36 ÷ 10.4) + 1 = 4 rows.
  6. 6.Two of those rows hold 20 plants and two hold 19, for 78 — thirty percent more than the square grid, because the row spacing dropped from 18 in to 10.4 in as well as the offset being applied.
  7. 7.The pure geometry gain from offsetting alone, at identical neighbour spacing, is 15.5%.
  8. 8.At 50 cents a plant, filling the bed costs $30.

Result: 60 plants in a square grid — 78 if the rows are offset

The same bed as square-foot gardening at 6 in both ways

  1. 1.Same bed, but nobody walks between the rows, so the between-row spacing drops to the in-row figure of 6 in.
  2. 2.The margin drops to 3 in — half the spacing — leaving 234 in by 42 in usable.
  3. 3.Plants per row = floor(234 ÷ 6) + 1 = 39 + 1 = 40.
  4. 4.Rows = floor(42 ÷ 6) + 1 = 7 + 1 = 8.
  5. 5.Total = 320 plants, or 4 per square foot — which is exactly the square-foot gardening figure for a 6 in crop such as lettuce or bush beans.
  6. 6.Against the 60 plants the row layout fitted, the same ground now holds more than five times as many.
  7. 7.Almost all of that comes from not leaving walking room, not from crowding the plants — every plant still has its 6 in.

Result: 320 plants — 4 per square foot, and the plants are no closer together

The 15% you get for free

A square grid is the obvious way to lay out plants and it is not the densest one. Offsetting alternate rows by half a space, and closing the rows up accordingly, fits 15.5% more plants into the same ground with every plant still exactly the same distance from its nearest neighbour.

The geometry is straightforward. In a square grid each plant sits at the corner of a square of side s, and occupies s² of ground. In a triangular arrangement each plant sits at the vertex of an equilateral triangle of side s, the rows sit s×√3⁄2 apart, and each plant occupies s²×0.866. Divide one by the other and the density ratio is 1 ÷ 0.866 = 1.155.

This is the same packing that makes hexagons appear in honeycomb and in stacked oranges, and it is why orchards, vineyards and container nurseries are laid out that way. It is not crowding: the nearest-neighbour distance is unchanged, so each plant has exactly the same room its label asked for.

The cost is a few minutes of setting out. Mark the first row normally, then start the second row half a space in and pull it closer by the 0.866 factor. After two rows the pattern is obvious enough to continue by eye.

Why row spacing is bigger than plant spacing

Seed packets and plant labels usually give two numbers, and the second is almost always larger. "Sow 4 inches apart in rows 18 inches apart" describes a plant needing 4 inches and a gap of 18, which is not a description of the plant at all.

The row gap is for access. Field agriculture is laid out for machinery, and home gardening inherited the convention with a person substituted for the tractor. Eighteen inches is roughly what a foot needs; thirty inches is what a wheelbarrow needs.

In a raised bed reached from the side, nobody ever walks between the rows, so the entire justification disappears. The in-row spacing can be used in both directions, and the bed suddenly holds three to five times as many plants — not because the plants have been crowded, but because the paths have been removed.

This is the whole insight behind square-foot gardening, and the 1, 4, 9, 16 grid is just in-row spacings of 12, 6, 4 and 3 inches applied in both directions. It also explains the four-foot bed width: two feet is about as far as most people can comfortably reach, so four feet is the widest bed that never needs standing in.

What crowding actually costs

Spacing recommendations describe the mature plant, which means every correctly spaced bed looks embarrassingly empty on planting day. The temptation to fill the gaps is strong and it is the wrong instinct.

Crowded plants compete first for light. A plant shaded by its neighbours puts energy into growing taller rather than into fruit, and the result is a tall, thin, unproductive stand. They then compete for water and nutrients in the same volume of soil, so everything dries out faster and needs feeding more often.

The problem that ends up doing the damage, though, is air. Dense foliage holds humid air against leaves, and most fungal diseases — powdery mildew, early blight, botrytis — need extended leaf wetness to establish. A crowded tomato bed is a reliable way to get blight; the same plants at the right spacing frequently escape it entirely in the same season.

Thinning is the corrective and it is genuinely difficult to do. Pulling healthy seedlings feels like waste, and the yield from a correctly thinned row is reliably higher than from an unthinned one. Cutting at soil level with scissors rather than pulling avoids disturbing the roots of the keepers.

Where the general rules break

A few situations override the arithmetic on this page.

  • Vertical growing — a caged or trellised tomato occupies a fraction of the ground a sprawling one does, and cucumbers, beans and squash on supports change from 36 in spacing to 12. Going up is by far the biggest density gain available in a small garden — considerably more than the 15% from offsetting.
  • Intercropping — a fast crop between a slow one uses ground that would otherwise be bare. Radishes between broccoli are finished before the broccoli needs the space, so the bed effectively holds both.
  • Succession — spacing describes one crop at one moment. A bed cleared of spring lettuce and replanted with beans has held two crops at full spacing, which no per-square-foot figure captures.
  • Perennials and shrubs — spacing is for the mature size after several years, not the pot it arrived in. This is where over-planting is most costly, because the correction involves removing established plants rather than thinning seedlings.
  • Wind and pollination — sweetcorn is wind-pollinated and needs a block at least four rows deep rather than a single long row, regardless of what the spacing arithmetic prefers.

What this assumes, and where it stops

Assumptions

  • Plants sit at both ends of each row, so the count is a floor division plus one.
  • The triangular layout uses a row spacing of in-row spacing × √3⁄2 and offsets alternate rows by half a space.
  • Offset rows hold one fewer plant than aligned rows, since they start half a space in from the end.
  • The margin is applied on all four sides of the bed.
  • Spacings in the crop table are typical published figures and vary by cultivar.

Limitations

  • Vertical growing changes ground-area requirements far more than layout does, and none of it is modelled here.
  • Intercropping and succession planting both put more crops through a bed than any single-layout calculation can represent.
  • Irregular beds, curves and obstructions are not handled — divide an awkward bed into rectangles and add the results.
  • Recommended spacings vary between cultivars, and between determinate and indeterminate forms of the same crop.
  • Sunlight, soil quality and water availability all affect how closely plants can actually be grown, and none of them appear in a geometric calculation.

Common questions

How many plants fit in a square foot?

At 12 in spacing, one; at 6 in, four; at 4 in, nine; at 3 in, sixteen. That is the square-foot gardening grid, and it works because a bed reached from the side needs no walking room between rows — the in-row spacing is used in both directions rather than leaving an 18 or 30 in path.

Does triangular plant spacing really fit more plants?

Yes, 15.5% more at exactly the same neighbour spacing. In a square grid each plant occupies spacing squared; in a triangular grid, with alternate rows offset half a space and rows closed to spacing × 0.866, each plant occupies 86.6% of that. It is the same packing that gives honeycomb its hexagons, and it is why orchards and nurseries are laid out that way.

What is the difference between plant spacing and row spacing?

Plant spacing is what the mature plant needs; row spacing is usually what a person needs to walk down. Field agriculture leaves 18 to 30 inches between rows for access, and home gardening inherited the convention. In a raised bed reached from the side nobody walks between rows, so the row gap can collapse to the in-row spacing.

Can I plant closer than the packet says?

You can, and it usually costs more than it gains. Crowded plants compete for light and grow tall rather than productive, dry out faster, and hold humid air in their foliage — which is what powdery mildew and blight need. The exception is growing vertically: a trellised plant occupies far less ground than a sprawling one and can legitimately be spaced much closer.

How wide should a raised bed be?

Four feet if it is reached from both sides, two feet if it is against a wall. Most people can comfortably reach about two feet, and the whole point of a raised bed is soil you never stand on — a bed wider than your reach forces you into it, compacting the soil you built the bed to protect.

How far in from the edge should the first plant go?

About half the in-row spacing is a sensible default — 6 inches in for a 12 inch crop, 3 inches for a 6 inch crop. That gives an edge plant roughly the same share of ground as a middle one, since it only has neighbours on one side.

Sources

Formula and content last reviewed on .

Results are estimates for information only, not professional advice.

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