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...
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.
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?