What size terrarium do I need for a leopard gecko or ball python?

Keeper communities commonly cite a 36" x 18" footprint (roughly 34–50 gallon) as a solid adult leopard gecko home, and a 48" x 18" x 18" (4ft) enclosure for an adult ball python. Always verify the front-door gap is escape-proof for smaller animals, a recurring complaint flagged on some PVC and budget models.