About TerraGlass

Building a terrarium is a small exercise in guesswork the first time around. How deep should the drainage layer really be for this jar? How much soil actually fits once the layers are in? Will six ferns crowd a 30cm bowl, or is that too few? Is this bathroom-shelf spot humid enough for moss, or does the lid need to stay on tighter? How much sheet moss do you actually need to cover the floor? None of these questions are hard on their own, but eyeballing every one of them, for every jar, is where a simple hobby starts to feel fiddly.

TerraGlass exists to take that guesswork off your plate. Instead of long articles you have to read end to end, the site is built around a set of small, single-purpose calculators, each aimed at one part of the build. The Substrate Layer Ratio Calculatorsplits your container’s height into drainage, charcoal, substrate, and top-dressing depths. The Jar & Vessel Volume Calculatorworks out a cylinder, sphere, bell jar, or rectangular tank’s total and usable volume. The Plant Count Calculator estimates how many plants of a given mature spread will fit your floor area at a chosen density. The Terrarium Humidity Guide gives moss, ferns, and air plants a target humidity range and a suggested misting cadence for your room. The Moss Coverage Calculator figures out how many pads or fragments you need, and how long a sparser planting takes to fill in. And the Drainage Layer Calculator sizes the reservoir at the bottom of the jar so roots never sit in standing water.

Beyond the calculators, the blog and learn section cover layering, plant choices, and vessel selection in plain language, and the Museum of Glass Gardens is a browsable collection of terrariums and bottle gardens, moss and ferns, air plants and epiphytes, and the vivariums and glasshouses that shaped the wider history of gardening under glass, with every entry, image, and fact drawn from Wikipedia and Wikimedia Commons.

A few things worth stating plainly. TerraGlass is an independent site, built for hobbyists and decor enthusiasts, and is not affiliated with any nursery, garden centre, or plant retailer. It is supported by advertising, which is how the tools stay free with no account required. Every number the tools produce is a planning estimate built on standard hobbyist ratios and the figures you enter, not a horticultural guarantee — real terrariums vary with light, room temperature, and the specific plants you choose. This site is for hobby and decor purposes only and makes no claims about plant safety or toxicity; if a container will share a home with pets or curious children, research the specific plants involved before adding them. If something looks off in a tool or an article, or a calculator is missing that would help, the contact page is the place to say so.