Loan Plant Spacing Estimator
Plant tags say "space 12 inches apart" and beds come in square feet — the conversion between the two is where nursery orders go wrong. Enter the bed area and the spacing: get the plant count on a square grid, and on the staggered layout the pros use, spares included.
Spacing is centre-to-centre at the plant's mature size, from the tag — spacing for today's pot size is how beds turn into jungles by July of year two. For several beds, add their areas together.
How it works
On a square grid each plant owns a square of spacing × spacing: plants per sq ft = 144 ÷ spacing². At 12-in spacing that is exactly 1 plant per sq ft; at 6 in, 4 per sq ft — the count quadruples when spacing halves, which is why ground-cover quotes shock people. A staggered (triangular) layout offsets each row: each plant effectively owns 0.866 of the square, so the same bed fits about 15.5% more plants (the 1.1547 factor) and closes cover faster with no plant closer to a neighbour than the grid allows. A 10% spare allowance covers the inevitable dud in every flat.
Formula & worked example
Formula: Plants per sq ft = 144 ÷ spacing² on a square grid; a staggered (triangular) layout multiplies density by 1.1547. Total = ceil(area × density × (1 + spare allowance)).
Worked example: A 100 sq ft bed at 12-in square spacing: 110 plants with 10% spares. A 200 sq ft bed at 18-in staggered spacing takes 113.
When to use this
- You are filling a new bed and the nursery sells by the flat or pot.
- You are planting ground cover and the per-square-foot count is the whole budget.
- You are laying out a vegetable garden at tag spacing.
How to use it, step by step
- Measure the bed area in square feet (length × width).
- Choose the spacing from the plant tag — mature size, not pot size.
- Pick square grid for vegetables, staggered for cover and massing.
- Keep the spare allowance — flats always contain a dud.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Bed area | Planting area in square feet | 40 sq ft border; 100–200 sq ft beds |
| Spacing | Centre-to-centre distance | 6 in ground cover; 12 in perennials; 24–36 in shrubs |
| Layout | Square grid or staggered triangular | Tri fits ~15% more plants |
| Spare allowance | Extra plants for failures | 10% standard |
Another worked example
A 200 sq ft bed planted staggered at 18-in spacing: density is 144 ÷ 324 × 1.1547 = 0.51 plants per sq ft, so the bed takes 113 plants with spares. The same bed on a square grid at 18 in would take 98 — the staggered premium buys the faster, fuller close-in.
Frequently asked questions
How many plants do I need for a 100 sq ft bed?
At 12-in spacing on a square grid: 100 plants, 110 to buy with the 10% spare allowance. Staggered at the same spacing, the bed fits about 128 — the fuller layout is a real 15% more plants, not a rounding error.
How many ground-cover plants per square foot?
At 6-in spacing, 4 per sq ft — a 100 sq ft bed is a 440-plant order with spares. At 9 in, about 1.78 per sq ft; at 12 in, 1. Flats of plugs are priced assuming you know this arithmetic.
Grid or staggered?
Staggered for ground cover and massed perennials — the offset rows close gaps faster and look natural sooner. Grid for vegetables and anything you cultivate between, where straight rows earn their keep. A 200 sq ft bed at 18-in staggered spacing takes 113 plants.
What spacing for tomatoes and peppers?
Tomatoes 24–36 in (indeterminates at the wide end, with airflow being the real point); peppers 18–24 in; lettuce and herbs 6–12 in. The tag's number assumes full sun and average soil.
Should I plant tighter for instant effect?
You can — clients do it all the time for a season-one show — but budget to divide or remove every other plant in year two or three. Plants do not negotiate; they just compete.
🌱 Covering the ground between plants?
Plants counted, finish the bed: the Mulch Calculator sizes bark or compost cover for the same area — and the Stone Estimator prices the permanent version.
How do I plant a hedge instead?
Hedges use linear spacing along a line: most screening shrubs plant at ½ to ⅔ of their mature width (a 6-ft-wide shrub at 3–4 ft centres). Run this estimator per row with the row's length × a nominal 1-ft width only as a rough cross-check.
What if the tag gives a spacing range?
Plant at the wide end for low maintenance and air flow, the tight end for fast cover in a high-visibility bed. The count difference between 12 and 15 in on 100 sq ft is about 40 plants — a real budget decision, not a detail.