Plant Spacing Calculator: How Many Plants Will Fill Your Bed?

Plants per 100 square feet

At the same spacing, a staggered bed needs about 15% more plants than a square grid: 116 instead of 100 at 12 inches, 52 instead of 45 at 18 inches. Find your spacing in the first column and multiply by your bed size in hundreds of square feet.

The square-grid figures from 6 to 18 inches match the University of Illinois Extension planting chart for ground covers. I calculated the staggered column and the 24 and 36 inch rows myself, rounding up to whole plants, since nobody plants 0.3 of a hosta.

The chart and the diamond pattern don’t match

Here is the catch. Illinois Extension tells you to plant ground covers in a staggered or diamond pattern for best results, but its plant counts work out exactly to a square grid: 100 square feet divided by one square foot per plant at 12 inches.

Buy 100 plants from that chart and set them 12 inches apart in a diamond pattern, and they cover only about 87 square feet. You run out with roughly 13% of the bed still bare. There are two fixes. Buy the staggered number, or keep the chart’s count and widen the spacing slightly. One hundred plants staggered across 100 square feet sit about 12.9 inches apart, which is the same plant budget spread a different way.

Why staggered rows fill in faster

Staggered planting leaves smaller bare patches for the same number of plants. In a 12 inch square grid, the spot farthest from any plant sits in the middle of each square, about 8.5 inches from the nearest stem. Put the same 100 plants on 100 square feet in a staggered layout and that farthest spot is about 7.4 inches away.

That inch matters while a ground cover is filling in. Illinois Extension says to allow one to two growing seasons for a planting to become completely established, and that 1 to 2 inches of mulch reduces weed growth and keeps the soil moist in the meantime. Smaller gaps mean less bare mulch for weeds to find.

Marking out staggered rows

Set the rows closer together than the plants. For a staggered layout the gap between rows is the spacing times 0.866, and every other row shifts sideways by half a space.

• 6 inch spacing: rows about 5.2 inches apart, alternate rows shifted 3 inches.
• 12 inch spacing: rows about 10.4 inches apart, shifted 6 inches.
• 18 inch spacing: rows about 15.6 inches apart, shifted 9 inches.

Each plant then sits the full spacing from its six neighbors, and the calculator prints the row gap for any spacing you enter.

Edges change the count in a small bed.

A 10 by 10 foot bed at 12 inches needs 116 staggered plants by area, but if you keep every plant half a space in from the edges only 11 rows fit, alternating 10 and 9 plants, for 105 in all.

I added that fitted count to the calculator for rectangles because the area figure overbuys in narrow strips and small beds; in a square grid at 12 inches the two methods agree, at 100 plants.

What spacing to put in the plant spacing calculator

Use the spacing on the plant tag first, and the mature spread if the tag gives no spacing. Illinois Extension says spacing depends on the plant’s habit, rate of growth, cost and how fast the area needs to be covered, with faster growers set further apart than slow ones.

Closer is the honest answer when you need coverage fast. Illinois warns that ground covers sold as easy, rapid coverage in sun, shade, wet or dry can turn into aggressive problems, and suggests closer planting of better behaved ground covers instead. My guide to ground cover for shade sorts the shade options by soil and flags the ones that spread too far.

Plenty of gardeners go denser than any tag. A spacing thread on r/gardening that drew about 200 upvotes opened with:

“Does anyone else just completely disregard spacing recommendations in their garden beds? I’ve only been gardening for the last couple of years, but it seems like the more plants I cram into my beds, the happier everyone is (plants and myself included).”
– r/gardening, May 2026 (201 upvotes)

The trade-off came up in a different thread, on r/NativePlantGardening, where a reply explained what the tag number is for:

“The idea is that is the distance where when they’re “full grown” the edges of each plant will touch. It’s important if you care about each plant looking like an individual object. Many plants do better at higher densities, but there is the risk of disease when there’s less airflow and it can be harder to weed/maintain.”
– r/NativePlantGardening, March 2026 (25 upvotes)

Hostas are the case where one number won’t do. Illinois Extension’s hosta page gives spacing from 12 inches to 3 feet depending on variety, and says plants spread one to five times their height, so check the cultivar in the best hostas for shade before you pick a spacing.

Spacing two different plants side by side

Tags assume a bed full of one plant. When neighbors have different spacings, add half of each: a plant tagged at 18 inches next to one tagged at 8 inches goes 9 + 4 = 13 inches away. That rule comes from the same r/NativePlantGardening thread:

“What I do is divide that “18” spacing by two. Now, you have the radius of the plant, 9″. If another plant says spacing of 8″ I would again, cut it by half. 4″ Now, I want to plant the bellwort by that random smaller one. Add the two radius together, and it’s 13″ So, you can safely plant those about 13″ apart.”
– r/NativePlantGardening, March 2026 (71 upvotes)

It works because tag spacing is measured center to center, at the distance where two mature plants of that kind just touch, so half of it is one plant’s reach. For a mixed bed, the calculator gives a rough count if you enter the average spacing of the plants you’re mixing.

Plant spacing questions