Bulb Spacing Calculator — How Many Bulbs Fit in a Bed
Enter the length and width of your planting bed and the desired spacing between bulbs to instantly find out the number of rows, columns and total bulbs you need to fill the area evenly.
m
m
cm
14 rows × 21 columns at 15 cm centres
- 1
Spacing in metres
15 cm ÷ 100 = 0.15 - 2
Columns along length
⌊3 ÷ 0.15⌋ + 1 = 21One bulb at each edge, then one every spacing interval. - 3
Rows along width
⌊2 ÷ 0.15⌋ + 1 = 14 - 4
Total bulbs
14 rows × 21 columns = 294
How does this calculator work?
For a bed of Length × Width metres with bulbs spaced S cm apart: Columns = floor(L / (S/100)) + 1, Rows = floor(W / (S/100)) + 1, Total bulbs = Rows × Columns. A 3 m × 2 m bed at 15 cm spacing holds 21 × 14 = 294 bulbs.
Formula
How this is calculated
Bulbs are planted on a regular grid: one bulb at each edge, then one every spacing distance inward. The number of columns along the length equals the floor of (length ÷ spacing) plus 1 (for the edge bulb), and the rows along the width follow the same logic. The total count is simply rows × columns.
Typical spacing recommendations by bulb type: small bulbs such as grape hyacinth (muscari) and crocus, 5–8 cm; mid-size bulbs such as tulips and daffodils, 10–15 cm; large alliums, 20–30 cm; dahlias, 30–45 cm. Plant the bulbs at a depth of roughly two to three times the bulb's diameter. Closer spacing gives a denser, more dramatic display but requires replanting or thinning after a few seasons as the bulbs multiply.
This calculator uses a simple rectangular grid. For triangular offset planting (each row staggered by half a spacing), the effective density increases by about 15%: multiply the rectangular count by 1.15 as a rough estimate. The bed dimensions are entered in metres and spacing in centimetres for convenience; the calculator converts internally.
Frequently asked questions
Tulips are typically planted 10–15 cm apart centre to centre for a full, lush look, or 20 cm for a more formal spaced planting. Closer spacing (10 cm) gives the maximum floral impact but costs more bulbs. For a 1 m × 1 m bed at 10 cm spacing, you need about 121 bulbs.
A square grid places each bulb directly behind the one in the previous row. Offset planting staggers each alternate row by half a spacing, fitting more bulbs into the same area (about 15% more) and creating a more natural look. Use the grid count from this calculator and add 10–15% for an offset layout.
The general rule is to plant at a depth of 2–3 times the bulb's maximum diameter. A tulip bulb 4 cm wide should be planted 8–12 cm deep. Bulbs planted too shallow are frost-prone; too deep and they may struggle to emerge.
TG we-Calculate Editorial Team. (2026). Bulb Spacing Calculator — How Many Bulbs Fit in a Bed [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bulb-spacing-calculator
TG we-Calculate Editorial Team. "Bulb Spacing Calculator — How Many Bulbs Fit in a Bed." TG we-Calculate. 2026. https://we-calculate.com/calculator/bulb-spacing-calculator.
TG we-Calculate Editorial Team, "Bulb Spacing Calculator — How Many Bulbs Fit in a Bed," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bulb-spacing-calculator
@misc{wecalculate_bulb_spacing_calculator, title = {Bulb Spacing Calculator — How Many Bulbs Fit in a Bed}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bulb-spacing-calculator}}, year = {2026}, note = {TG we-Calculate} }
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