Bulb Calculator
How many bulbs do you need — or how much bed will the bulbs you bought fill? Pick a bulb type to get depth, spacing, and count.
6–8" deep, 4–6" apart (Iowa State University Extension)
Prefilled from the sourced range midpoint — adjust if you want them tighter or looser.
You need
184bulbs
- Planting depth
- 6–8 in
- Per sq ft
- 5.76
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How deep and how far apart to plant bulbs
Fall-blooming bulb depth and spacing varies by type, mostly driven by bulb size — bigger bulbs like daffodils and alliums go deeper and farther apart than small ones like crocus and grape hyacinth. When a source doesn't give an exact depth for a variety, Iowa State University Extension's rule of thumb is to plant a bulb roughly 2 to 3 times as deep as the bulb itself is tall.
Spacing follows the same logic: small bulbs can sit close together for a dense drift of color, while large bulbs need room so the mature plant isn't crowded. Use the table below as a starting point, and lean toward the tighter end of a range for a fuller-looking planting.
| Bulb | Depth | Spacing |
|---|---|---|
| Tulip | 6–8 in | 4–6 in |
| Daffodil | 6–8 in | 6 in |
| Crocus | 3–4 in | 3 in |
| Allium (large) | 6 in | 12–18 in |
| Hyacinth | 6 in | 6–8 in |
| Grape hyacinth | 3–4 in | 2 in |
Bottom line: match depth and spacing to bulb size — small bulbs shallow and close, large bulbs deep and spread out.
How many bulbs fit a given bed
Bulb count scales with the square of spacing, not the spacing itself, so tightening spacing by a little packs in a lot more bulbs. A 4×4 ft bed (16 sq ft) shows the swing across the calculator's supported bulb types below.
| Bulb | Spacing used | Bulbs needed |
|---|---|---|
| Tulip | 5 in | 92 |
| Daffodil | 6 in | 64 |
| Crocus | 3 in | 256 |
| Allium (large) | 15 in | 10 |
| Hyacinth | 7 in | 47 |
| Grape hyacinth | 2 in | 576 |
Bottom line: small bulbs like crocus and grape hyacinth need hundreds per bed at close spacing; large bulbs like allium need a fraction as many.
Naturalizing vs. formal spacing
A formal, evenly-spaced grid (what this calculator assumes) suits borders and rows along a walkway. For a more natural drift look — common with daffodils and crocus in a lawn or under trees — gardeners typically scatter bulbs by hand and plant them where they land, which uses roughly the same total bulb count as an even grid at the same average spacing, just distributed less uniformly.
How it's calculated
- 1
Pick a bulb type
Tulip, daffodil, crocus, allium, hyacinth, or grape hyacinth — each has its own sourced depth and spacing range.
- 2
Choose a mode
"A bed to fill" converts your bed size into a bulb count. "This many bulbs" converts a bulb count into the area it will cover.
- 3
Read your result
Spacing sets bulbs per square foot ((12 ÷ spacing in inches)²); the calculator multiplies or divides by your bed area accordingly.
Frequently asked questions
How deep do you plant tulip bulbs?
6 to 8 inches deep, per Iowa State University Extension. That's measured to the base of the bulb, with the pointed end up.
How many tulip bulbs per square foot?
At the commonly recommended 4-6 inch spacing, that works out to roughly 4-9 bulbs per square foot using a square-grid layout — tighter spacing (4 in) fits more, wider spacing (6 in) fits fewer.
When should I plant tulip bulbs?
Fall, 6-8 weeks before the ground freezes, so roots establish before winter — the same general timing as garlic and other hardy bulbs.
How many bulbs do I need for a bed?
Multiply your bed's square footage by bulbs-per-square-foot for your chosen spacing (12 ÷ spacing in inches, squared). This calculator does that math for six common fall bulb types.