Plant Count Calculator
Give the floor area and a plant’s mature spread, pick a planting density, and see how many will comfortably fit.
Recommended plant count
Planning around growth, not just today
It's tempting to count how many small starter plants fit in a jar today, but the useful number is how many will fit once they've reached their mature spread. A terrarium planted to its full mature count usually looks sparse at first and fills in beautifully over the following months — planting to today's small size instead almost always leads to overcrowding later.
Mixing plants of different mature sizes works well: use the calculator once per plant type, treating each as if it had the whole floor to itself, then divide the floor between them roughly in proportion to how many of each you want.
Frequently Asked Questions
How is the plant count worked out?
Each plant's mature canopy is treated as a circle sized by its spread, and the calculator works out how many of those circles fit into the portion of the floor area you've chosen to plant (not the whole footprint — some floor is always left for paths, hardscape, or breathing room between plants).
What's the difference between the three densities?
Sparse reserves most of the floor as open substrate or hardscape, with just a few accent plants — good for a minimalist or moss-forward layout. Moderate fills a comfortable middle ground. Full aims for a dense, jungle-style planting where foliage nearly touches, which looks lush faster but crowds plants sooner as they grow.
Where do I find a plant's mature spread?
Nursery tags and plant databases usually list a mature width or spread. If you can't find one, measure a mature specimen of the same species, or use a conservative estimate — it's easier to add a plant later than to remove a crowded one.
Why did I get a count of zero?
That means even one plant at its full mature spread wouldn't fit in the density you've chosen for that floor area. Try a smaller-spreading plant, a larger vessel, or a fuller density setting.
Decor and planning guidance only — a geometric estimate, not a guarantee of how any specific plant will grow in your conditions. This tool makes no claims about plant safety or toxicity.