Gardeners Toolkit
Free UK planting layout calculator

Plant Spacing Calculator

Turn a supplier's spacing recommendation into a practical plant count for a bed, border or repeated planting area — including square grids, staggered layouts and separate row spacing.

Square & staggered gridsRows + in-row spacingNo invented plant database
Comparison of square and staggered plant spacing patternsSquare gridStaggered gridspacingspacingSame spacing value, different geometry

Use the spacing for the plant you are actually buying

The calculator does the layout maths; it does not decide what a particular species needs. Check the plant label, nursery guidance or mature spread, then enter that centre-to-centre spacing here.

Why this matters

RHS guidance for perennials recommends using the predicted mature spread as the starting point and notes that planting too closely increases competition. The tool therefore keeps spacing fully editable rather than pretending one number suits every plant.

Calculate plant numbers

Choose the method that matches how you are planning the bed. For an irregular border, measure its area first and use the area-estimate mode.

Spacing guide
Step 1

Choose the calculation method

Each bed is calculated separately before totals are added.
Area estimate

Estimate from area and spacing

Area mode is a density estimate. It is useful for curved or irregular beds, but it cannot know exactly how individual plants will land at the boundary. For precise rectangular row/column counts use a layout mode.

Rectangular grid

Lay plants out in a square or staggered grid

Default: half-spacing inset. With 50 cm spacing, plant centres start about 25 cm from the edge, avoiding the unrealistic assumption that a plant centre sits exactly on the border.

Rows

Use different spacing between rows and along each row

Your planting estimate

Estimated total—

—

Bed area—
Layout—
Plants per m²—
Rows—
Plants per row—
Edge method—
Spacing is an input, not a recommendation.

Check the label or nursery guidance for your chosen plant. Mixed borders, paths, access gaps and irregular edges can change the final order.

You have the plant count — plan the bed around it

Use the next tool that matches the job rather than starting the measurements again.

Check the spacing methodSquare grids, staggered planting, rows and centre-to-centre measurement.Measure an irregular bedSplit an awkward border into shapes and bring the total area back here.Calculate compost for the bedTurn the same bed area into litres and whole bags.Filling a raised bed?Calculate its internal soil volume separately.

What this calculator does differently

Plant quantity is not just an area-division problem. A theoretical density is useful for a large planting area, but a real rectangular bed also has boundaries. The grid modes therefore count rows and planting positions, while the area mode stays clearly labelled as an estimate.

edge insetBoundary-aware grid countHalf-spacing inset keeps plant centres inside the bed instead of placing them on the border line.
centre spacingStaggered layoutRows are offset. In a large area, triangular packing has a higher theoretical density than a square grid at the same centre spacing.

Centre-to-centre spacing is the number that matters

Measure from the centre of one plant to the centre of the next. Pot width is not the same thing as mature spacing. RHS perennial guidance advises checking the predicted spread or width and using that as the starting point; it also notes that plants may be set a little closer if the aim is for them to knit together, while overly close planting increases competition.

Square grid, staggered grid or rows?

A square grid uses the same spacing horizontally and vertically. A staggered or triangular grid offsets alternate rows; its theoretical row spacing is about 0.866 times the centre spacing. A row layout is different again because spacing along the row and spacing between rows can be set independently.

Theoretical density: square grid = 1 ÷ spacing². Staggered grid = 1 ÷ (spacing² × 0.866). Actual bed counts can be lower because edges and access gaps remove planting positions.

How the edge setting changes the count

The default half-spacing inset places the first row of plant centres half a spacing inside the boundary. For a 4 m × 2 m bed at 50 cm square spacing, that produces 8 positions along the length and 4 across the width: 32 plants. Choosing “plant centres at edges” instead counts positions on both boundary lines and produces a larger number. Neither method is universally correct; the bed design decides which is appropriate.

Irregular and mixed borders need judgement

For an irregular border, calculate the total area with the Garden Area Calculator and use area mode as a first estimate. If the bed contains shrubs, drifts, bulbs, access gaps or several species with different mature spreads, a scaled sketch is often more useful than forcing the whole border into one density. RHS bedding guidance similarly recommends planning more complicated shapes to scale rather than relying only on a rectangular calculation.

Common plant-count mistakes

  1. Using the pot diameter as the planting distance instead of the recommended mature spacing.
  2. Multiplying area by a plant density without allowing for the bed edge, paths or deliberate gaps.
  3. Assuming a staggered grid uses the same row spacing as a square grid.
  4. Using one spacing for a mixed border containing plants with very different mature spreads.
  5. Ordering from a calculator before checking the nursery or plant-label recommendation.
Sources behind the guidance

RHS guidance on planting perennials explains using predicted spread as a spacing starting point. Its bedding-plant guidance describes row/column calculations for regular blocks and scaled planning for complicated shapes.

Useful next step

Read the Plant Spacing Guide for the plants-per-square-metre reference table, layout diagrams and a worked border example. For the calculation rules themselves, see How our calculations work.

Planning a hedge rather than a bed?

Linear hedge runs use a different counting method, including single and staggered double rows.

Open hedge calculator
Check the measurement referenceKeep units, area and linear measurements consistent.