Bulb Spacing Calculator
Plan your spring display, one bulb at a time.
Garden Bed & Spacing
RESULT
Triangular layout · 25 sq ft · 6 in spacing
Your Planting Layout
Illustrative pattern preview. Area mode assumes a square bed for display.
Area-based estimate, rounded up. Paths, obstacles and edge setbacks are excluded; actual planting positions can differ. Denser is not always better for the variety.
Calculation & Worked Example
Area per center is s² in a square grid, or √3/2 × s² in an equilateral triangular grid. Adjacent staggered rows are s × √3/2 apart. These are interior density formulas, not an exact finite-bed packing solver.
Suggested spacing and depth are editable examples. Bulb size, variety, soil and local climate determine appropriate planting guidance.
Frequently Asked Questions
What does this bulb spacing calculator estimate?
It divides planting area by the area allocated to each bulb center. The result is a rounded-up planning quantity, not a guarantee that exactly that many centers fit inside a particular boundary.
Which values should I enter?
Enter your plantable bed area, rectangle dimensions or circle diameter, and the center-to-center distance on your bulb package. Exclude paths and other unplanted spaces. Extra allowance changes the order quantity only.
How does triangular spacing change the estimate?
Alternating rows shift sideways by half the center spacing. The row gap is √3/2 times that spacing, so interior density is 2/√3, or about 15.47%, higher than a square grid. Finite-bed counts and rounded totals need not differ by exactly 15.47%.
How deep should I plant my bulbs?
Use the bulb package or a variety-specific guide. RHS guidance generally relates depth to bulb height, rather than prescribing one depth for every bulb. This planner measures the example depth from soil surface to bulb base; changing depth does not change the density calculation.
More questions (8)
Why can my actual layout need fewer bulbs?
Edges, irregular shapes, setbacks, access routes and existing plants change usable positions. The density formulas treat the area as an interior grid. Mark out a small section and check the border before ordering for a small or narrow bed.
What does center-to-center spacing mean?
Measure from the middle of one planting position to the middle of the next. It is not the gap between bulb skins. In triangular mode the nearest-neighbor distance remains the entered spacing; the perpendicular row gap is smaller.
Does changing units change my plan?
No. Feet and inches are converted using 1 ft = 0.3048 m and 1 in = 2.54 cm. Internal physical values are retained through unit switches, so switching repeatedly does not change the estimated quantity.
Why is the result rounded upward?
Whole bulbs must be ordered. The base estimate is rounded up once, and an optional allowance is applied to that whole-bulb quantity and rounded up separately. For 116 bulbs with 10% extra, the order estimate is 128 bulbs.
Can I plan circular beds and borders?
Circle mode uses π × (diameter/2)². Rectangle mode works for a straight border using its length and width. Irregular beds can be divided into simpler parts or entered through net total area. Curved borders and tree rings with an excluded center are not exact shapes in this version.
Are garlic and ornamental alliums interchangeable?
No. Ornamental Allium species and edible garlic differ substantially in plant size, spacing and depth. The Alliums card is an ornamental example, not a garlic recommendation. Enter the spacing and depth from the exact species or cultivar instructions.
Does the preview show every bulb?
It illustrates the pattern and flower type. Large beds display a labeled representative section to keep the drawing readable and fast. Flower artwork shows appearance only; it does not predict bloom timing, mature plant size or a surveyed planting map.
How can I save or share my plan?
Copy planting summary copies the active measurements, pattern, estimates and assumptions. Download plan saves the same information as a text file. Verify the species guidance and local growing conditions before using the plan.
Sources & References
Royal Horticultural SocietyBulb planting, depth and variety guidance
University of Minnesota ExtensionBulb selection, planting and seasonal careSources provide horticultural context, not endorsement of this calculator or its example presets.
Plan bulb quantities for square or triangular spacing, with rectangle, circle and net-area inputs, flower examples and a live planting preview.