Free plant decor calculator
Terrarium Supply Calculator
Estimate drainage, soil, charcoal, moss, plants, and starter budget for an open or closed terrarium before you buy too much filler or the wrong container.
Affiliate note: This page may contain affiliate links. If you buy through these links, we may earn a commission at no extra cost to you. Always verify plant needs, container size, drainage, toxicity around pets, and seller details before buying terrarium supplies.
Use this as a planning estimate. Closed terrariums need less airflow and usually prefer moisture-loving plants. Open terrariums are better for succulents, cacti, and drier display builds.
Estimated terrarium supply plan
How to use this terrarium estimate
Start with the container dimensions, then build in layers: drainage, charcoal if needed, soil or substrate, moss/top dressing, plants, and decorative pieces. The calculator rounds up because most supplies are sold in bags, jars, or bundles instead of exact cups.
Closed terrariums
Use moisture-friendly plants, moss, small ferns, fittonia, and a light hand with watering. Avoid succulents in sealed humid containers.
Open terrariums
Use grittier mix, better airflow, and plants that tolerate drier conditions. Succulents and cacti usually want bright light and less water.
Fantasy display terrariums
Keep one focal piece first, then add moss, stones, miniature doors, mushrooms, crystals, or tiny path material. Too many pieces make the scene look like clutter instead of a designed miniature world.
Before you buy
- Check mature plant size so the terrarium does not outgrow itself immediately.
- Use activated charcoal for closed humid builds, especially when airflow is limited.
- Keep drainage depth reasonable. A huge rock layer steals root space.
- For pet homes, verify plant safety before bringing anything indoors.
- For outdoor/patio displays, check weather exposure and whether miniatures will fade or rust.
Planning a fantasy plant corner? Pair this with the fairy garden planner, LED strip light calculator, and outdoor rug size calculator.