Bulb Planting Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
The number of bulbs is calculated by fitting a regular grid onto the bed: (⌊length ÷ spacing⌋ + 1) × (⌊width ÷ spacing⌋ + 1). For a 2 m × 1 m bed with bulbs spaced 15 cm apart, you need 98 bulbs.
Explanation
Planting spring-flowering bulbs (tulips, daffodils, crocuses, grape hyacinths) at a regular spacing is the same geometric problem as planting vegetables in a garden bed, already covered by our vegetable garden plant spacing calculator: it isn't a matter of dividing the total area by the spacing squared, which would systematically underestimate the real number of bulbs, but of counting an actual grid of rows and columns, each starting at an edge of the bed. That's why the number of rows equals the length divided by the spacing, rounded down, PLUS ONE (the first bulb in a row sits right at the origin, before even the first gap) — a classic calculation pitfall if that "+1" gets forgotten. The recommended spacing varies significantly by bulb type and the desired look: tighter spacing (5 to 8 cm) for small bulbs like crocuses or grape hyacinths creates a dense carpet effect, while wider spacing (10 to 15 cm) for tulips or daffodils gives each plant room to grow without directly competing for nutrients. Planting depth follows a separate rule, independent of this calculator: generally two to three times the bulb's own height, information worth checking on the supplier's packaging for each variety.
Example: 2 m × 1 m bed, tulips spaced 15 cm apart
Inputs
Length: 2 m. Width: 1 m. Spacing: 15 cm.
Calculation
Rows = ⌊200 ÷ 15⌋ + 1 = 13 + 1 = 14. Columns = ⌊100 ÷ 15⌋ + 1 = 6 + 1 = 7. Total = 14 × 7 = 98 bulbs.
Result
You need 98 tulip bulbs to cover this bed at this spacing.
Frequently asked questions
Why add "+1" to the number of rows instead of simply dividing the length by the spacing?
Because the first bulb in a row sits right at the origin of the bed, before even the first gap of the chosen spacing. Simply dividing the length by the spacing would count the number of GAPS, not the number of bulbs: there's always one more bulb than gaps along a row, exactly like regularly spaced fence posts.
What spacing should I choose between bulbs?
It depends on the bulb type and the look you want: tight spacing (5 to 8 cm) for small bulbs like crocuses gives a dense, natural carpet effect, while wider spacing (10 to 15 cm) for larger bulbs like tulips or daffodils gives each plant room to grow. The supplier's packaging always states a precise recommendation for the variety purchased.
How deep should bulbs be planted?
The general rule, independent of this calculator, is to plant a bulb at a depth of roughly two to three times its own height: a large tulip bulb is therefore planted deeper than a small crocus bulb. Like spacing, this is always stated on the packaging for the specific variety purchased.
Should a bulb bed be fertilized after planting?
A moderate application of fertilizer rich in phosphorus and potassium (rather than nitrogen, which favors foliage at the expense of flowering) is often recommended at planting and again the following spring, to help the bulb rebuild its reserves after flowering. See our fertilizer dosage calculator to work out the right amount for the bed's area.