How to measure for your plant spacing project
- Measure your bed area. Measure length and width in feet and multiply. For an irregular bed, split it into rectangles, calculate each one, and add the totals. A winding border? Walk it in rough sections.
- Pick a spacing and layout pattern. Enter your plant-to-plant spacing in inches — measured center to center. Then choose square grid (straight rows) or triangular/staggered (every other row offset). Staggered fits about 15% more plants in the same space at the same spacing.
- Read the count and shop accordingly. The calculator returns total plants needed and plants per square foot. Round down to whole plants, then buy a few spares for losses and the odd gap at bed edges. Closer spacing fills in faster but raises upfront plant cost.
How the plant spacing calculator works
Convert spacing from inches to feet, square it to get the area each plant occupies, then divide the total area by that footprint — and multiply by the pattern factor. For a square grid the factor is 1; for triangular (staggered) rows it is approximately 1.1547 (= 2 ÷ √3), because the offset rows pack more centers into the same footprint. Example: 100 sq ft at 12-inch spacing on a square grid → spacing in feet = 1, area per plant = 1 × 1 = 1 sq ft, plants = floor(100 × 1 ÷ 1) = 100. Same bed, same spacing, triangular layout: plants = floor(100 × 1.1547 ÷ 1) = 115. At 6-inch spacing, square grid: spacing in feet = 0.5, area per plant = 0.25 sq ft, plants = floor(100 × 1 ÷ 0.25) = 400.
Which type are you estimating?
Square grid — simple rows and columns
Plants are set in straight rows aligned to a grid. Every plant is equidistant from its four nearest neighbors. This is the easiest pattern to stake out and the calculator default.
Enter: Enter spacing in inches, select Square grid. For a 100 sq ft bed at 12 in: 100 plants.
Triangular / staggered — offset rows
Every other row shifts half a spacing width sideways. Each plant sits in the gap between two plants in the row ahead, so centers are closer together without crowding. Fits about 15% more plants at the same plant-to-plant distance — useful for groundcovers and mass plantings.
Enter: Enter spacing in inches, select Triangular. At 12 in over 100 sq ft: 115 plants vs 100 for square grid.
Groundcovers (6–12 in spacing)
Low, spreading plants such as creeping phlox, sedum, or ajuga. Tighter spacing fills gaps faster and suppresses weeds sooner, but the upfront plant count is high. At 6 in on a square grid you need 400 plants per 100 sq ft; at 12 in you need 100.
Enter: Area = your bed size, Spacing = 6 or 8 or 12 in, Layout = Triangular for fastest cover.
Annuals and perennials (12–18 in spacing)
Mid-size flowering plants — coneflowers, salvia, marigolds, daylilies. Most prefer 12–18 inches on center. At 18 in on a square grid you need 44 plants per 100 sq ft; a triangular layout at the same spacing gives 51.
Enter: Area = bed size, Spacing = 12–18 in depending on mature spread, Layout = either pattern.
Small shrubs (24–36 in spacing)
Compact shrubs — spirea, dwarf boxwood, ornamental grasses. At 24 in on a square grid you need 25 plants per 100 sq ft. Check the mature spread on the plant tag; it is better to space for mature size and mulch between plants now than to crowd them and rip half out later.
Enter: Area = bed size, Spacing = 24–36 in or the plant's listed mature spread, Layout = Square grid is easiest to stake out for shrubs.
Tips & ways to save
- Measure spacing center to center — not edge to edge. The gap between plants narrows as they grow, but the center-to-center distance stays fixed.
- Irregular or curved beds: divide the space into rough rectangles, run the calculator on each section, and add the counts together. It is better to slightly underestimate each section and buy a few spares than to over-order.
- Triangular spacing shines for mass plantings and groundcovers — it fills voids more evenly and produces a natural, less grid-like look, all while fitting about 15% more plants at the same spacing.
- Closer spacing fills in faster and suppresses weeds sooner, but raises upfront cost. A common compromise: plant at 12 in now, thin or transplant extras once the bed closes in after one full growing season.
- Always buy a few extras — 5–10% above the calculator total. Transplant shock and the occasional mystery death are part of gardening, and matching plants are easier to find at planting time than a month later.
Plants per 100 sq ft by spacing (square grid)
| Spacing | Plants per sq ft | Per 100 sq ft |
|---|---|---|
| 6 in | 4 | 400 |
| 8 in | 2.25 | 225 |
| 12 in | 1 | 100 |
| 18 in | 0.44 | 44 |
| 24 in | 0.25 | 25 |
Square-grid spacing. A triangular (staggered) layout fits about 15% more plants for the same spacing. Counts assume a rectangular area with no border allowance.
Frequently asked questions
How many plants do I need per square foot?
What is the difference between square and triangular spacing?
How far apart should I space ground cover?
How do I calculate plants needed for an irregular bed?
What does "spacing on center" mean?
How many plants do I need for 100 square feet?
Sources
Related calculators
Reviewed by the BackyardCalc editorial team. Figures are computed from the formula above and checked against manufacturer yields.