Plant Spacing Calculator
Calculate how many plants a garden bed needs from its dimensions, plant spacing and layout. Choose square, triangular or rectangular spacing, add a border allowance, estimate total plant cost, or work backwards from a target plant count to find the right spacing.
Formula
Worked example
A 120 x 48 in bed with a 2 in border and 12 in square spacing: effective area = 116 x 44 in. Plants per row = floor(116/12)+1 = 10, rows = floor(44/12)+1 = 4, total = 40 plants. Density = 40 / (116x44/144) = 40/35.4 = 1.13 plants/ft². At $3.50 per plant, budget $140.
How the plant count is worked out
The calculator first subtracts the border allowance from every edge to find the effective planting area. Then it counts how many plants fit along the length: one at the start plus one for every full spacing interval. It does the same across the width to find the number of rows, then multiplies the two. Because a plant sits at each end of every row, a bed that is a whole number of spacings long gains an extra plant on that edge, which is why the formula adds one. The rough area shortcut (length x width divided by spacing squared) ignores those edge plants and slightly undercounts small beds, so this calculator counts rows and columns directly. A border allowance keeps the outer plants away from the bed frame or path, which lets roots develop fully and prevents the first plant from leaning over the edge.
Square, triangular and rectangular layouts
A square layout aligns every plant in straight rows and columns, the simplest pattern to mark out, weed and harvest. A triangular (staggered) layout shifts every other row sideways by half a spacing so each plant nestles into the gap between two plants in the next row. This lets the rows sit about 0.866 of the spacing apart while keeping every plant the same distance from its nearest neighbours, fitting roughly 15% more plants into the same bed for the same crowding. A rectangular layout uses a separate in-row spacing (the gap between plants within a row) and a between-row spacing (the gap between row centres). This is common in field crops and hedgerows where you want narrow spacing within each row for efficiency but wide aisles between rows for machinery, a hoe or foot traffic. Set the between-row spacing to match your walking aisle width plus the plant width at maturity.
Reverse-solve: finding the spacing for a target plant count
If you are working from a budget or a fixed number of plug trays, you can switch to reverse mode, enter the total plants you need, and the calculator finds the square-grid spacing that comes closest to that count. It searches from a fine spacing up to the bed length and picks the spacing that minimises the difference between the actual and target count. The result will often not be an exact round number because whole rows and columns must fit, so the final count may be slightly above or below your target. Use the suggested spacing as a starting point, then adjust in forward mode if you need a specific multiple.
Estimating plant cost and planning purchases
Turn on the cost estimate and enter the price per plant, seedling or plug at your nursery. The total covers the plants the calculator says you need. In practice, buy 5 to 10% extra to cover transplant losses, especially for bare-root stock or tender annuals. If the cost total is too high, switch to a triangular layout to squeeze more plants in for the same spacing, or increase the spacing slightly and accept fewer plants. Seed-grown crops are far cheaper per plant: factor in thinning losses when converting a seed rate to a plant count.
Choosing the right spacing
Plant spacing is usually printed on the seed packet or plant label as a centre-to-centre distance that accounts for the mature spread of the plant and the airflow it needs to stay disease-free. Too tight and plants compete for light and water, stretch toward the sun and trap humidity; too loose and you waste bed space and invite weeds into bare soil. When a packet lists both in-row and between-row figures, use the larger value for a conservative single-spacing estimate, or enter them separately in rectangular mode. Subtract any paths, compost bays or unplanted borders from the bed dimensions before calculating so the estimate matches the area you will actually fill.
Typical spacing for common vegetables and herbs
| Crop | Spacing (in) | Spacing (cm) | Notes |
|---|---|---|---|
| Lettuce | 8-10 | 20-25 | Heads; 6 in for cut-and-come-again |
| Spinach | 6 | 15 | Thin to final spacing after germination |
| Carrots | 3-4 | 8-10 | Thin seedlings; rows 6 in apart |
| Radish | 2-3 | 5-8 | Fast-growing; succession-sow every 2 weeks |
| Bush beans | 6 | 15 | Rows 18 in apart in rectangular mode |
| Onions / shallots | 4-6 | 10-15 | Sets; from seed allow 1 in then thin |
| Kale / chard | 12-18 | 30-45 | Larger leaves need more room |
| Broccoli / cauliflower | 18-24 | 45-60 | Needs full spacing to form heads |
| Tomatoes (indeterminate) | 24-36 | 60-90 | Stake or cage; allow airflow |
| Courgette / squash | 36-48 | 90-120 | Sprawling habit; one or two per bed |
| Basil | 8-12 | 20-30 | Pinch flowers to extend harvest |
| Parsley | 8-12 | 20-30 | Slow germinator; thin to final spacing |
| Lavender | 18-24 | 45-60 | Perennial; needs good airflow |
| Strawberries | 12-18 | 30-45 | Runners need space to spread |
Centre-to-centre spacing for a square grid on a square grid; use the rectangular mode for field rows with separate in-row and between-row spacing. Always check the seed packet for the exact figure.
Frequently asked questions
Should I use square, triangular or rectangular spacing?
Square spacing is easiest to lay out and weed because plants line up in straight rows and columns. Triangular (offset) spacing staggers alternate rows so they sit about 87% of the spacing apart, fitting roughly 15% more plants for the same plant-to-plant distance, ideal for intensive beds of lettuce, spinach or root crops. Rectangular spacing uses a narrower gap within each row and a wider gap between rows, common for field crops where you need walking aisles or want to run a hoe between rows.
What does the border input do?
The border is the gap you leave between the bed edge and the first plant on every side. A 2-4 inch (5-10 cm) border keeps outer plants from leaning over the bed frame and lets their roots develop fully. It reduces the effective planting area, so the plant count drops slightly. Set it to zero if you plant right to the edge.
Why does the count add one plant per row?
A plant sits at each end of a row, so a row that is a whole number of spacings long holds one more plant than the number of gaps. For example, a 12-inch row at 4-inch spacing has three gaps but four plants. The simple area formula (area divided by spacing squared) ignores these edge plants and slightly undercounts, so this calculator counts rows and columns directly.
How does the reverse-solve mode work?
Enter the total number of plants you need and the calculator searches for the square-grid spacing that gets closest to that count. It tests thousands of spacing values and picks the one with the smallest difference between the actual and target count. Because whole rows and columns must fit, the final number of plants may be a few above or below your target. Use the suggested spacing in forward mode to verify and fine-tune.
How do I account for plant losses when buying?
Add 5-10% to the calculator result when ordering. Transplant losses are highest for bare-root stock, tender cuttings in cold soil, or seedlings planted in hot, dry weather. For slow-maturing crops such as brassicas or leeks, losses early in the season are costly, so a bigger buffer (10-15%) is worthwhile. Enable the cost estimate to see how the extra plants affect your budget.
Where do I find the recommended spacing for my plants?
The recommended spacing is printed on the seed packet or plant tag, usually as a centre-to-centre distance that accounts for the mature size of the plant and the airflow it needs to resist disease. If both an in-row and between-row figure are given, use rectangular mode and enter each separately, or use the larger value in square mode for a conservative single-grid estimate.