Plant Spacing Calculator
How many plants fit in your bed: square vs triangular layouts.
Spacing is the distance between plants in every direction. Not just along the row. Get it right and plants get the light, water, and airflow they need; get it wrong and they compete with each other, disease spreads faster, and yields drop. This calculator works out how many plants fit in any bed, in a square grid or in offset triangular rows, for 22 common crops.
It also tells you how many seeds to sow, because not every seed germinates. If you have not tested your seed yet, run the Seed Germination Calculator first. Then bring its rate back here. For the soil the bed needs, see the Raised Bed Soil Calculator.
How this is worked out
Square layout: columns = bed length ÷ spacing, rows = bed width ÷ spacing, plants = columns × rows, each rounded down to whole plants. Triangular layout: every other row is shifted by half a spacing, so rows pack tighter. About 15% more plants fit. Seeds to sow = plants wanted ÷ (germination rate ÷ 100), rounded up.
Assumptions:
- Spacing is the distance between plant centres, in every direction.
- The bed is rectangular and plants are not allowed to overhang the edge. Each plant needs its full spacing inside the bed.
- Triangular rows are an estimate at about 15% more than a square grid, following the offset-row comparison used by BloomingExpert’s Plant Spacing Calculator.
- Spacing values are typical. Varieties differ. A cherry tomato and a beefsteak tomato do not take the same space. So your seed packet is the final authority.
Three worked examples
1. Lettuce in an 8 × 4 ft bed at 8 in. Columns = 96 ÷ 8 = 12, rows = 48 ÷ 8 = 6, so 72 plants in a square grid, or about 82 in offset rows. At 85% germination, sow 72 ÷ 0.85 = 85 seeds.
2. Tomatoes in an 8 × 4 ft bed at 24 in. Columns = 96 ÷ 24 = 4, rows = 48 ÷ 24 = 2, so 8 plants. Eight tomato plants sounds like little. But each one grows into a bush several feet wide, and crowded tomatoes invite blight.
3. Carrots in a 4 × 4 ft bed at 3 in. Columns = 48 ÷ 3 = 16, rows = 16, so 256 carrots. At 85% germination, sow 302 seeds. Or sow thickly and thin to the spacing as seedlings appear.
Typical spacing for 22 crops
| Crop | Spacing | Plants per sq ft |
|---|---|---|
| Carrot | 3 in | 16 |
| Radish | 2 in | 36 |
| Beet, Onion, Beans (bush) | 4 in | 9 |
| Spinach | 6 in | 4 |
| Lettuce | 8 in | 2.25 |
| Kale, Basil, Herbs, Corn | 12 in | 1 |
| Pepper, Eggplant, Broccoli, Cabbage, Cauliflower | 18 in | 0.44 |
| Tomato | 24 in | 0.25 |
| Cucumber, Zucchini, Squash | 36 in | 0.11 |
These spacings follow the square-foot gardening method popularised by Mel Bartholomew: one square foot holds 1 tomato, 4 lettuces, 9 bush beans, or 16 carrots. This calculator applies the same idea to any bed size.
Common spacing mistakes
- Spacing by the seedling, not the adult plant. Seedlings look small and lonely in a bed. Space for the mature plant, and fill the gaps with quick crops like radish or lettuce that finish before the main crop needs the room.
- Ignoring airflow. Plants touching each other stay wet after rain, and wet leaves are where fungal disease starts. If you cannot fit your hand between mature plants, they are too close.
- Using row spacing as plant spacing. Seed packets often give a wider row spacing for walking between rows. In a raised bed you walk around the outside, so you can use the tighter plant spacing in every direction.
- Sowing exactly the number of plants you want. Not every seed germinates and not every seedling survives. Sow for the germination rate. The calculator does this for you.
- Forgetting the edge. A plant at the very edge of a bed still needs its full spacing. Leave half a spacing between the outermost plant and the bed frame.
What to do next
Lay out the bed on paper first: draw the grid, mark each plant, and count. Then check the soil with the Raised Bed Soil Calculator and the seed with the Seed Germination Calculator. Spacing, soil, and seed are the three numbers that decide whether a bed feeds you or frustrates you.
Putting the result to work
Use the spacing result as a planting map, not just a number. Draw the bed on paper, mark the grid, and put a dot for every plant. You will spot problems on paper that you would only notice in the bed when it is too late, like a tall tomato shading a row of lettuce behind it. Put tall plants on the north side of the bed (in the northern hemisphere) so they do not shade the short ones, and leave a walking gap of at least a foot between beds.
Succession sowing turns one spacing plan into a season of harvests: sow a row of lettuce every two weeks instead of the whole bed at once, and replace each finished row with the next crop. The same spacing math applies to every sowing. The bed does not care whether it is the first or the third planting. And when a crop finishes early, fill the gap immediately: bare soil loses moisture and invites weeds, while a quick catch crop like radish earns its space in three weeks.
How spacing works
- Spacing is the distance between plants in every direction. Not just along the row.
- Square layout: plants in a grid. Columns = bed length / spacing, rows = bed width / spacing, plants = columns x rows.
- Triangular (offset) layout: every other row is shifted half a spacing, so rows pack tighter. About 15% more plants fit.
- Seeds to sow = plants wanted / (germination rate / 100), rounded up. At 85% germination, 72 plants need 85 seeds.
- Choose a crop to fill in its typical spacing, or pick Custom spacing and enter your own.
Why does spacing matter?
Too close and plants compete for light, water, and nutrients, while airflow drops and disease spreads faster. Too wide and you waste bed space that could have fed you. Correct spacing is the cheapest yield increase in gardening: it costs nothing and it changes how much a bed produces.
Are these spacings exact?
No. They are typical values. Varieties differ: a cherry tomato and a beefsteak tomato do not take the same space, and a bush cucumber is not a vining cucumber. Always check your seed packet or variety description, and use the calculator’s custom spacing when the packet disagrees.
What is square-foot spacing?
It is the method popularised by Mel Bartholomew: divide a bed into one-foot squares and plant each square by the crop’s spacing. One tomato, four lettuces, nine bush beans, or sixteen carrots per square foot. This calculator uses the same idea for any bed size, not just four-by-four beds.
What is the difference between square and triangular layouts?
In a square layout, plants sit in a straight grid. In a triangular layout, every other row is shifted by half a spacing, so the rows pack tighter and about 15 percent more plants fit in the same bed. Triangular rows suit small plants like lettuce and carrots; large plants like tomatoes are easier to manage in a square grid.
How many seeds should I sow for the plants I want?
Divide the plants you want by your germination rate as a decimal and round up. For 72 lettuce plants at 85 percent germination, sow 72 divided by 0.85, which is 85 seeds. If you do not know your rate, test the packet first with the Seed Germination Calculator.
Spacing values are typical garden spacings (square-foot gardening method, Mel Bartholomew). Check your seed packet for the variety you are growing. Triangular-row gain of about 15% follows the offset-row comparison used by BloomingExpert’s Plant Spacing Calculator.
