Turtle Tank Size Calculator
Enter your turtle’s shell length and how many turtles you keep together to see the minimum recommended tank size in gallons.
What this calculator does
The Turtle Tank Size Calculator estimates how many gallons of water a pet turtle’s enclosure should hold, based on the widely used shell-length guideline.
How the recommendation works
A common rule of thumb among turtle keepers is 10 gallons of water per inch of shell length for the first turtle, since aquatic and semi-aquatic turtles need enough room to swim, turn around freely, and dive. Each additional turtle housed in the same tank is estimated to need about half again as much additional water volume, since turtles can share swimming space more efficiently than a single first turtle needs on its own.
- A 6-inch turtle needs roughly 60 gallons on its own
- Tank length should generally be at least 4 times the turtle’s shell length
A note on accuracy
Actual space needs vary by species (fully aquatic vs. semi-aquatic vs. terrestrial box turtles), so treat this as a general starting guideline rather than species-specific husbandry advice.