If I had to guess I'd say it's roughly 40x30" ballpark. I erred toward the larger size for stability and weight, since I planned on using it for squats and other greater resistance exercises. I had an old homemade wine rack laying unused in the basement, so I pulled off the front panel and used the wine glass slots to organize and store the bands, which worked out perfectly for holding two complete sets.
It works very well, wish I'd put this together a long time ago. It's too big to travel with, but for a home gym, or to keep in the office if you have space, it's a must have if you're even remotely handy with basic tools and using bands for training.
Edit to add: if you plan on building one, I recommend multiple attachment points front and back, as you'll find that some exercises benefit from anterior vs posterior attachment points, and vice versa. For example, squats work best with the lateral attachments, but the band ends up either underneath or on top of your feet, which is a trip hazard, so attaching the band to the eye centrally located eye bolt at the base, then running it up through the lateral attachment points moves the band away from the foot placement, and adds more tension in the squatting position. Attaching the bands to posterior lateral points versus the lateral points for deltoid raises adds more resistance all the way through the motion. You'll figure out quickly through experimentation which points work best for which exercises.
The devil made me do it the first time, second time I done it on my own - W
It works very well, wish I'd put this together a long time ago. It's too big to travel with, but for a home gym, or to keep in the office if you have space, it's a must have if you're even remotely handy with basic tools and using bands for training.
Edit to add: if you plan on building one, I recommend multiple attachment points front and back, as you'll find that some exercises benefit from anterior vs posterior attachment points, and vice versa. For example, squats work best with the lateral attachments, but the band ends up either underneath or on top of your feet, which is a trip hazard, so attaching the band to the eye centrally located eye bolt at the base, then running it up through the lateral attachment points moves the band away from the foot placement, and adds more tension in the squatting position. Attaching the bands to posterior lateral points versus the lateral points for deltoid raises adds more resistance all the way through the motion. You'll figure out quickly through experimentation which points work best for which exercises.
The devil made me do it the first time, second time I done it on my own - W