Gardening
Greenhouse Size Calculator
Enter length, width and optional shelf levels to see growing area and plants from spacing.
How big should a greenhouse be?
Greenhouse planning begins with floor length × width, then multiplies by usable shelf levels to estimate growing area. Extra shelf levels count as additional growing planes above the floor; paths still steal real planting space, so treat the total as an upper bound. Optional plant spacing (as a square grid) divides growing area by spacing² for a rough plant count. Staging width, pot size and crop height matter more than the raw number once you start fitting benches. Soil volume for beds can be checked with raised bed soil; outdoor spacing uses plant spacing.
Worked example
3 × 2 m floor = 6 m². One extra shelf level → 12 m² growing area. At 0.3 m spacing → spacing² = 0.09 → about 133 plant spaces.
Limits and assumptions
Shelves assumed fully usable. Does not model shade cloth, surplus heat or guttering.
Frequently asked questions
What counts as an extra shelf level?
Each additional usable tier above the floor. Floor only = 0 extras (multiplier 1×).
Should paths be excluded?
Ideally measure only planting width, or reduce length/width to the cultivated footprint.
Square spacing only?
Yes — rectangular spacing needs manual area per plant (row × in-row).
Is taller better than wider?
Shelves add area without a bigger footprint, but height and light falloff limit how many tiers help.