Free tool

Plant Spacing Calculator

This plant spacing calculator counts how many plants fit your bed, tent or room at a chosen spacing, in a square or triangular layout. Add your light to compare with published yields.

Plants that fit

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The other layout: —
Space per plant: —

Next: Work out the light for the plants you can fit

How it works

Every plant sits half a spacing from the walls, so its leaves stay inside the bed. In a square grid, rows and columns are one spacing apart.

In a staggered (triangular) layout, each row is shifted half a spacing along, so every plant is the same distance from its six neighbours. The rows are then only 0.87 of a spacing apart, which can fit more rows in a deep bed.

Formula

Square:     plants = ⌊L ÷ s⌋ × ⌊W ÷ s⌋
Staggered:  rows = ⌊(W − s) ÷ (s × √3/2)⌋ + 1
            odd rows ⌊L ÷ s⌋, even rows ⌊L ÷ s − ½⌋
L and W after taking off the edge gap on both sides

What a plant spacing calculator counts

Spacing is the distance from the centre of one plant to the centre of the next. The calculator also keeps every plant half a spacing from the walls, so its leaves stay inside the bed. The result is the number of whole plants that really fit, not floor area divided by space per plant.

The difference is large in small beds. In a 4×4 ft tent at 0.82 ft (25 cm), area alone suggests about 23 plants. Only 16 fit in a square grid and 20 in a triangular one, because the outer plants need room to the wall. The “Space per plant” line then divides the whole floor by the plants that fit: 1 ft² each for 16 plants, 0.8 ft² for 20.

Plant spacing formula: square and triangular

In a square grid, each row holds the length divided by the spacing, rounded down, and there are as many rows as the width allows. In a triangular (staggered) layout, rows sit 0.87 of a spacing apart and every other row is shifted half a spacing along, so it can hold one plant fewer.

Which wins depends on the bed. On a 100 × 100 ft field at 2 ft, triangular fits 2,822 plants against 2,500, about 13% more. In a 4×4 ft tent at 2 ft it fits 3 against 4. The calculator always shows both, so you can pick the better one for your space.

How many plants fit in a 4×4 tent

For a 4×4 ft floor (1.49 m²) with no edge gap:

2 ft apart: 4 square, 3 triangular.
1.5 ft apart: 4 either way.
33 cm (9 per m²): 9 square, 12 triangular.
1 ft apart: 16 square, 14 triangular.
25 cm (16 per m²): 16 square, 20 triangular.

More plants do not always mean more harvest. In a Belgian density study, 16 and 20 cannabis plants per m² gave the same yield per m².

Other tents behave the same way. At 2 ft apart, a 2×4 holds 2, a 4×8 holds 8, a 10×10 holds 25, and a 5×5 holds only 4, no more than a 4×4. Close the 5×5 to 1.5 ft and it holds 9.

Vegetable plant spacing and sea of green

The crop buttons fill in published spacings: staked tomatoes and peppers 18 inches apart in the row (Cornell), leaf lettuce 10 inches (8–12, Mississippi State) and basil 12 inches (University of Maryland). For a sea of green, the 16 per m² button sets 25 cm.

One catch: 18 inches is the distance along a garden row, and rows are usually further apart. Used both ways in a grid, it gives each tomato 2.25 ft². For greenhouse tomatoes, Mississippi State gives 4 to 5 ft² each, about 2–2.2 ft apart, so use that in a bed or tent.

Using the result, and common mistakes

Measuring edge to edge. Measure stem to stem.
No room to reach. Set an edge gap for a walkway or to reach the back; it comes off both sides. An 8×8 ft bed at 2 ft holds 16 plants, but with a 1 ft gap all round it holds 9.
Reading the yield box as a forecast. It shows what two studies measured. At an average of 600 µmol/m²/s, the LED study’s line gives about 231 g/m², or 344 g for a 4×4 ft tent, whether you grow 4 plants there or 16.

To find the PPFD for that box, use the LED grow light calculator, or the PPFD to DLI calculator if you have a meter reading.

FAQ

Questions growers ask

How many plants fit in a 4×4 grow tent?

4 at 2 ft apart, 9 at 33 cm (9 per m²) and 16 at 25 cm (16 per m²) in a square grid. A triangular layout fits 12 and 20 at those last two spacings. Each plant sits half a spacing from the walls, so these are whole plants that really fit.

What is the plant spacing formula?

Square: plants = (length ÷ spacing, rounded down) × (width ÷ spacing, rounded down). Triangular: rows sit 0.87 of a spacing apart, and every other row is shifted half a spacing. Simple area ÷ spacing² overcounts small beds, because the outer plants need half a spacing to the wall.

Is plant spacing measured centre to centre?

Yes. Spacing is the distance from the middle of one plant to the middle of the next, not the gap between leaves. The calculator also keeps each plant half a spacing from the walls, so a 2 ft spacing leaves 1 ft between the outer stems and the tent side.

How many autoflowers fit in a 4×4 tent?

We found no published spacing for autoflowers. The density study we use tested 9 to 20 cannabis plants per m². In a 4×4 ft tent (1.49 m²), that is 9 plants at 33 cm or 16 at 25 cm in a square grid. Choose the closer spacing only if your plants stay small.

How much space does a sea of green need?

About 25 cm (10 in) between plants, which is 16 plants per m². A Belgian study found 16 and 20 plants per m² gave the same yield per m², so packing tighter added plants but not harvest. In a 4×4 ft tent that is 16 plants square or 20 triangular.

How many plants per square foot?

One at 12 inches apart, because a square foot is 144 square inches and each plant takes spacing × spacing. At 18 inches each plant takes 2.25 ft², about 0.44 per square foot; at 10 inches it is about 1.44. Small beds fit fewer, since outer plants need room to the wall.

What spacing should I use for tomatoes and peppers?

18 inches apart in the row for staked tomatoes and peppers, the Cornell figure the presets use. In a greenhouse, Mississippi State gives tomatoes 4 to 5 square feet each, about 2–2.2 ft apart both ways. In a bed or tent with no paths, the wider spacing is the safer start.

Square or staggered?

A staggered (triangle) layout puts every other row half a space along, so plants sit the same distance from all their neighbours. In a deep bed it can fit a few more plants; in a narrow one the shifted rows can lose one plant each, so compare both.

Sources

The formulas and target ranges on this page come from these references.

Mississippi State University Extension: Greenhouse tomatoes, how many plants can I grow? (4 to 5 square feet per plant). extension.msstate.edu/agriculture/crops/commercial-horticulture/greenhouse-tomatoes/how-many-plants-can-i-grow
Reiners, S. (2017). Recommended spacing and expected yield for garden vegetables in New York. Cornell Cooperative Extension (staked tomato 18 in in the row; peppers 18 in). dlc.cce.cornell.edu/pluginfile.php/376627/mod_resource/content/1/Recommended%20Spacing%20and%20Expected%20Yield%20for%20Garden%20Vegetables%20in%20NY.pdf
Mississippi State University Extension: Garden planting guide (leaf lettuce 8–12 in between plants). extension.msstate.edu/lawn-and-garden/vegetable-gardens/planting-guide
University of Maryland Extension: Growing basil in the home garden (12 inches between plants). extension.umd.edu/resource/growing-basil-home-garden
Vanhove, W. et al. (2011). Yield of indoor cannabis cultivation (YILCAN), Belgian Science Policy: 16 and 20 plants per m² gave the same yield per m²; 9, 12 and 16 per m² also tested. belspo.be/Belspo/organisation/Publ/pub_ostc/Drug/rDR56synth_en.pdf
Rodriguez-Morrison, Llewellyn & Zheng (2021). Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment. Frontiers in Plant Science 12, 646020 (yield kept rising with DLI up to about 78). doi.org/10.3389/fpls.2021.646020
Potter & Duncombe (2011). The effect of electrical lighting power and irradiance on indoor-grown cannabis potency and yield. Journal of Forensic Sciences 57, 618–622 (0.9 to 1.6 g per watt under HPS). doi.org/10.1111/j.1556-4029.2011.02024.x

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