GardenCalcs.uk
Bulb Planting Calculator — How Many Bulbs Do I Need
Work out bulb quantities, planting depths, and spacing for displays.
Bed or border area to fill in m² — for an irregular shape, split it into rectangles and add the parts together.
Sets the recommended spacing and depth — e.g. daffodils 15 cm apart / 15 cm deep, crocuses 8 cm apart / 8 cm deep (RHS: plant 2–3× the bulb's height).
Normal gives a solid block of colour (~44 daffodils or ~69 tulips per m²); choose Sparse for a naturalised drift or Dense for a packed bedding display.
Density multiplier for sparse/naturalised planting (default 0.6)
Density multiplier for dense/packed display (default 1.5)
Extra percentage for replacements and failures (default 0%)
How We Calculate This
Bulb count is based on the recommended spacing for each type, with density adjustment.
Formula: Bulbs per m² = (1 ÷ spacing²) × density multiplier. Total = Area × Bulbs per m².
Planting depth follows the standard rule of 2-3× bulb height for most species.
Frequently Asked Questions
General rule: plant at 2-3 times the bulb height. Daffodils and tulips: 15 cm. Crocuses: 8 cm. Alliums: 15 cm.
Plant most spring-flowering bulbs in September-November. Tulips are best planted in November to reduce tulip fire disease risk.
For a good display: daffodils 40-50/m², tulips 50-60/m², crocuses 100-150/m². For naturalising, use fewer bulbs in random patterns.
Yes. Plant at the same depth as in the ground. You can layer different bulbs (lasagne planting) for a longer flowering display.
Lasagne planting layers different bulbs at different depths in the same pot. Plant large bulbs (tulips) deepest, medium (daffodils) in the middle, and small (crocus) near the top for months of colour.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.