What this calculator does
Find out how many plants to buy for your garden bed. Seed packets and plant tags give a spacing, such as 12 inches apart. They don't say how many plants that means for your bed. Buy too few, and weeds fill the gaps. Buy too many, and the plants get crowded. They then compete for light, water and air, and get sick more often.
This calculator lays plants out the way a gardener would. The outer plants sit half a spacing in from the edges. Then the plants go in a square grid of rows and columns, or in triangular rows. In triangular rows, every second row shifts over half a spacing, so the plants nest into the gaps. The calculator counts the plants that really fit and shows the rows and plants per row. It also gives a simpler estimate based on area alone, for comparison.
Where it's used
Why this math matters outside the classroom:
- Vegetable beds. Gardeners planting lettuce 12 in apart in a 10 × 4 ft bed fit 10 plants in each of 4 rows, or 40 plants.
- Offset rows. For 12 in triangular spacing, the rows sit √(12² − 6²) = 10.39 in apart, the height of an equilateral triangle.
- Bulb orders. Someone planting tulips 6 in apart in a 5 × 2 ft border fits 10 per row in 4 rows, so orders 40 bulbs.
- Landscape bids. Landscapers count ground-cover plugs for a client's slope before pricing the plants and the labor to set them.
- Geometry class. Students compare square and hexagonal packing and see why offset rows hold about 15% more circles in a large area.
Grade level and standards: Grades 7–8; Common Core State Standards for Mathematics 8.G.B.7. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the length and width of the bed in feet.
- Enter the spacing in inches from the seed packet or plant label. That's the distance from the center of one plant to the center of the next.
- Choose a square grid or offset triangular rows.
- Read the plant count. Then use the rows and plants per row to mark out the bed.
What the inputs mean
- Plant spacing (center to center)
- The distance from the center of one plant to the center of the next. When a label gives a range, the smaller number fills in faster. The larger one leaves more room for each plant to grow.
- Layout
- A triangular layout (also called offset or staggered) puts each plant the same distance from all six neighbors. So a large area holds about 15% more plants at the same spacing. In a narrow bed, the shorter offset rows can cancel out that gain.
Formula and method
plants per row = floor(length ÷ spacing) square grid: rows = floor(width ÷ spacing); plants = plants per row × rows triangular: row gap = spacing × √3 ÷ 2; rows = floor((width − spacing) ÷ row gap) + 1 triangular: offset row = floor(length ÷ spacing − 0.5); plants = full rows × per row + offset rows × offset row area-only estimate = area ÷ spacing² (square) or area ÷ (spacing² × √3 ÷ 2) (triangular)
floor means round down to a whole number, because you can't plant part of a plant. √3 ÷ 2 is about 0.866. The calculator converts all lengths to inches first.
The outer plants sit half a spacing from the edge. That gives them the same room as the inner ones. So a row holds length ÷ spacing plants, rounded down.
In a triangular layout, any three neighboring plants form a triangle with equal sides. So the rows sit closer together than the spacing. The gap between rows is the height of that triangle. Rows take turns: a full row, then a row shifted by half a spacing. The shifted rows can hold one fewer plant.
Worked example
A 10 × 4 ft raised bed planted at 12 in spacing in a square grid.
- Bed in inches: 120 × 48 in.
- Plants per row: 120 ÷ 12 = 10.
- Rows: 48 ÷ 12 = 4.
- Plants: 10 × 4 = 40.
Result: 40 plants fit, one per square foot. With offset triangular rows, the same bed holds 38. The four rows still fit, but two of them lose a plant to the half-spacing shift.
Understanding the result
The count is the number of plants to buy, or seedlings to grow, for this layout. Add a few spares if you expect to lose some to transplanting or pests.
When the triangular count is higher than the square count, the offset layout uses the space better. For long, narrow beds, a square grid is often just as good, and easier to mark out.
The area-only estimate is what many charts and quick formulas give. It ignores the edges, so it runs high for small beds. It gets closer to the grid count as the bed gets larger.
Assumptions and limitations
- The bed is a rectangle and every plant gets the same spacing.
- Outer plants sit half a spacing from the edge of the bed.
- Rows run along the length of the bed.
- It doesn't plan paths, mixed plantings or plants that need different spacing.
- Curved or irregular beds need to be split into rectangles and added up.
- Spacing advice varies by variety and growing method. Follow the guidance for your plant.
Frequently asked questions
Is triangular spacing better than square spacing?
Over a large area, yes. An offset layout fits about 1.15 times as many plants at the same spacing. The even gaps also help ground cover fill in. In a small or narrow bed, the difference is small or even reversed. So compare both counts.
Should plants go right up to the edge of the bed?
Planting about half a spacing in from the edge gives the outer plants the same room as the inner ones. Maybe the bed sits beside a lawn or path you don't mind them spilling over. Then you can plant a little closer to the edge.
How do I turn the spacing into plants per square foot?
In a square grid, divide 144 by the spacing in inches squared (the spacing times itself). 12 in spacing gives 1 per ft², 6 in gives 4 and 4 in gives 9. Triangular spacing fits about 15% more over a large area.
Does this work for bulbs and ground cover?
Yes. Enter the recommended spacing for the bulbs or plugs (small starter plants) and the size of the area. The count works the same way. Bulbs are often planted in loose clusters instead, so treat the result as a guide.
How this calculator is checked
Method: Grid layout with plants half a spacing from each edge; triangular row pitch from the height of an equilateral triangle (spacing × √3 ÷ 2), with alternate rows offset by half a spacing. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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