How do you calculate the terrarium size needed for a lizard?

Question

The Backstory:

Complete pet newbie here, so bear with me please. A good friend of mine has a bearded dragon and asked me to look after it for a couple days while he was out of town. I'm the type of person that likes to approach any situation armed with as much knowledge as possible, so naturally I did some reading on bearded dragons. I've never owned any pets before and had never had much desire to, but I found that I enjoyed just watching his bearded dragon eat and ... glare at everything. A bit more research later and I discovered that lizards and other reptiles are relatively low maintenance, compared to say, a dog or cat. Which brings me to...

The Plan:

I'm seriously considering getting a small- to medium-sized lizard, and building a habitat for it (I'm a semi-pro craftsman). I have a limited amount of wall space in my house to put a vivarium up against, so I was considering a floor-to-ceiling design, with live plants inside. The dimensions of the enclosure I'm envisioning would be about 36" wide, 26" deep, and 72" tall, with some amount of soil at the bottom. The 72" height would probably be from the "ground", so the overall height might be closer to 84-86". By keeping the depth to 26" overall it should fit through any doorway. In terms of reptile species, I had looked at the Emerald Swift and I like it, and preliminary reading suggests they like to climb things, but I'm open to other possibilities.

The Question:

Is there a formula for calculating how many gallons the enclosure should be based on the length/size of the reptile? Or, is this different for each species? How does being vertically-oriented affect the "usable" space?

Answer 1

Short answer: Not really, because it all depends on the reptile and how active the species is.

Basically, there are going to be two options for the type of terrarium you would use. Long or tall.

A long terrarium is one that's going to be wider than it is tall. Those are the ones that look like fish aquariums (although the glass is thinner than an aquarium).

These terrariums are used for ground dwelling reptiles such as bearded dragons, various skinks, and leopard geckos. Since these reptiles spend their lives running on the ground, to forage for food and shelter, they benefit more from having the ground area to run around on.

A tall terrarium is one that's simply going to be taller than it is wide. Tall terrariums typically differ from the long terrariums in that they also have doors in the front for easier access.

These terrariums are used for arboreal reptiles such as swifts, iguanas, most frogs, and most geckos. Since these reptiles spend their lives climbing up and down trees, not often travelling in-between trees, they benefit more from the vertical area to climb around in.

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Once you know what shape of terrarium your lizard will benefit from most, you have to figure out what size will work best. This depends partly on the size of the reptile, but also on how active the reptile is.

Yes, the larger the reptile is the bigger the terrarium it will need, but don't be fooled by some of the smaller reptiles. Both skinks and swifts for example, will require a 30-gallon terrarium, where some similar sized reptiles, such as leopard geckos, will be fine in a 15-20 gallon terrarium.

I would suggest choosing a reptile first, and then asking for the recommended terrarium size. Otherwise, err on the side of caution and get a larger terrarium than you might think.