Ground Cover Plants Per Square Foot Tables

Ground cover plants per square foot is the number you need before you order plants for a bed, and this blog gives that number in imperial tables only, with the plant counts and the flat counts beside each density.

How to read the tables in this blog

Table 1 gives the density for each spacing, in plants per square foot and in plants per acre, for a square grid and for a triangular layout. Table 2 gives the plant count and the flat count for 100 sq ft in a square grid, with 5 percent extra and flats of 18. The imperial defaults are rounded equivalents of the metric defaults, not exact conversions.

The formula for plants per square foot

Plants per square foot in a square grid equals 144 divided by the spacing in inches squared, because 12 times 12 equals 144. At 12 in spacing, the sum is 144 divided by 144, which equals 1 plant per square foot. At 6 in spacing, it is 144 divided by 36, which equals 4. At 18 in spacing, it is 144 divided by 324, which equals 0.44 when shown to 2 decimal places. Plants per acre equals plants per square foot times 43,560. At 12 in spacing, that gives 43,560 plants per acre. A triangular layout, also called a staggered layout, fits more plants into the same area at the same spacing. Its density equals the square grid density divided by 0.8660254. The uplift is 1 divided by 0.8660254, which equals 1.1547, so a triangular layout needs 15.47 percent more plants than a square grid at the same spacing. The Ground Cover Calculator applies the same formulas. Plants always round up to a whole plant, and flats always round up to a whole flat.

How the extra percentage and the flats work

The extra percentage is an allowance for losses. The default extra is 5 percent, and the calculator allows 0 percent to 50 percent in steps of 0.1 percent. Plants equal area times plants per square foot times 1 plus the extra percentage, rounded up. At 5 percent extra, the multiplier is 1.05. Flats equal plants divided by plants per flat, rounded up. The default plants per flat is 18, and the calculator allows 1 to 200. Enter 1 for individual pots. A higher extra percentage does not always mean more flats, because the plant count can rise inside the same flat.

Worked example: 100 sq ft at 12 in spacing

The page imperial example covers 100 sq ft with plants 12 in apart in a square grid, with 5 percent extra and flats of 18. Plants per square foot equals 144 divided by 144, which equals 1. Plants equal 100 times 1 times 1.05, which equals 105. Flats equal 105 divided by 18, which is 5.833, rounded up to 6 flats. So the order is 105 plants and 6 flats of 18. Mulch for the same area is 16.4 cu ft at the calculator depth shown as 2 in in imperial. The spacing default is 12 in, and the area default is 100 sq ft.

Table 1: imperial densities by spacing

Spacing	Plants per sq ft square	Plants per sq ft triangular	Plants per acre square	Plants per acre triangular
6 in	4.00	4.62	174,240	201,195
8 in	2.25	2.60	98,010	113,172
12 in	1.00	1.15	43,560	50,299
15 in	0.64	0.74	27,878	32,191
18 in	0.44	0.51	19,360	22,355
24 in	0.25	0.29	10,890	12,575

How to use Table 1

Start with the spacing, then read across the row for the layout you plan to use. At 12 in spacing, a square grid needs 1.00 plant per square foot and a triangular layout needs 1.15, with per acre figures of 43,560 and 50,299. The per acre figures are densities, not order quantities on their own. To turn a density into an order, work the plant count for your own area, apply the extra percentage, round up, and then work the flats. The page FAQ values match Table 1: 1 plant per square foot at 12 in, 4 at 6 in, and 0.44 at 18 in, all in a square grid. The Plants per Square Foot Calculator uses the same square grid method, and the Plants per Acre Calculator gives the same per acre method.

Table 2: plant counts at 100 sq ft, square grid, 5 percent extra, flats of 18

Spacing	Plants	Flats of 18
6 in	420	24
8 in	237	14
12 in	105	6
15 in	68	4
18 in	47	3

How to use Table 2

Table 2 is the order for 100 sq ft in a square grid, with 5 percent extra and flats of 18. At 6 in spacing, the order is 420 plants and 24 flats, from 100 times 4.00 times 1.05, and 420 divided by 18, rounded up. At 12 in spacing, the order is 105 plants and 6 flats, as worked in full above. A small change in spacing makes a large change in the order. Moving from 12 in spacing to 6 in spacing quadruples the plant count, from 105 plants to 420 plants.

Triangular counts at 100 sq ft

The triangular counts at 100 sq ft, with 5 percent extra and flats of 18, are 485 plants and 27 flats at 6 in spacing, 273 plants and 16 flats at 8 in spacing, 122 plants and 7 flats at 12 in spacing, 78 plants and 5 flats at 15 in spacing, and 54 plants and 3 flats at 18 in spacing. Triangular at 12 in gives 122 plants against 105 plants in a square grid, which is 17 more plants, and 7 flats against 6 flats.

Scaling the order to larger areas

Table 2 covers 100 sq ft. At 12 in spacing in a square grid, with 5 percent extra and flats of 18, the order is 53 plants and 3 flats for 50 sq ft, 263 plants and 15 flats for 250 sq ft, 525 plants and 30 flats for 500 sq ft, and 1050 plants and 59 flats for 1000 sq ft.

Flats of 18, 32, and 36

Flats of 18 are the default in this blog. The page example of 105 plants needs 6 flats of 18, 4 flats of 32, and 3 flats of 36. The Plant Spacing Calculator covers a single spacing for plants in a bed, without flats or an extra percentage.

Mulch in imperial units

Mulch is given at the calculator depth shown as 2 in in imperial. For 100 sq ft, the volume is 16.4 cu ft. For 250 sq ft, the volume is 41.0 cu ft or 1.52 cu yd. For 500 sq ft, the volume is 82.0 cu ft or 3.04 cu yd. For 1000 sq ft, the volume is 164.0 cu ft or 6.08 cu yd. Cubic yards are shown only at 27 cu ft and above, because one cubic yard equals 27 cu ft. The Mulch Calculator gives mulch volumes for other areas.

How to use the calculator

First, measure the area to plant. Second, choose a ground cover or enter its spacing. Third, choose a square or staggered layout. Fourth, enter plants per flat, or 1 for individual pots.

What the calculator does not give

The calculator gives plant counts, flats, densities, and a mulch volume at the calculator depth only, from area, spacing, layout, plants per flat, and extra percentage. It gives no plant cost, no seed count, no yield figure, no fertiliser rate, no watering figure, no soil volume, and no coverage time in days or weeks.

The page assumptions

Spread rate varies with soil, light, and variety. Closer spacing gives faster cover at higher cost. Remove perennial weeds before planting.

Frequently asked questions

Q: How many ground cover plants per square foot?
A: At 12 in spacing in a square grid, 1 plant per square foot. At 6 in spacing, 4 plants per square foot. At 18 in spacing, 0.44 plants per square foot.

Q: How do I work out plants per square foot from spacing in inches?
A: Divide 144 by the spacing in inches squared. At 12 in spacing, 144 divided by 144 equals 1 plant per square foot.

Q: How many plants do I need for 100 sq ft at 12 in spacing?
A: 105 plants in a square grid with 5 percent extra, which is 6 flats of 18.

Q: How many more plants does a triangular layout need?
A: 15.47 percent more plants than a square grid at the same spacing. At 12 in spacing on 100 sq ft, a triangular layout needs 122 plants against 105 plants in a square grid, which is 17 more plants.

Q: How many flats of 18 do I need for 100 sq ft?
A: It depends on spacing. At 6 in spacing, 420 plants need 24 flats. At 12 in spacing, 105 plants need 6 flats. At 18 in spacing, 47 plants need 3 flats.

Q: How much mulch do I need for 100 sq ft of ground cover?
A: 16.4 cu ft at the calculator depth shown as 2 in in imperial. For 1000 sq ft, the volume is 164.0 cu ft or 6.08 cu yd.