Turtle Tank Size Calculator
Enter your turtle's adult shell length, how many turtles you keep, and the gallons-per-inch guideline you want to use. The calculator returns a planning volume. There is no single universal minimum, so check species-specific advice from a reptile veterinarian.
Last updated: September 25, 2026
Frequently asked questions
Is 10 gallons per inch of shell a legal or scientific minimum?
No. It is a widely repeated hobby guideline. This calculator lets you change it because there is no universal requirement, and some species need considerably more space than a simple rule suggests.
Should I size the tank for my turtle's current size or adult size?
Adult size. Hatchlings grow quickly, and planning for the adult avoids repeated upgrades. Use the adult shell length for your species.
How do I measure shell length?
Measure the straight-line carapace length from front to back, not over the curve of the shell. Enter it in inches or centimeters.
Why add extra volume for each additional turtle?
Turtles need room to swim, bask, and avoid each other. The extra percentage is adjustable, and some keepers prefer separate tanks for species that are aggressive.
Does tank volume replace filtration and a basking area?
No. Aquatic turtles also need a dry basking spot with proper heat and UVB lighting and strong filtration. Volume is only one part of the setup.
Where can I compare with other pet housing tools?
The Rabbit Cage Size, Rat Cage Size, and Dog Crate Size calculators cover other pets, though each species has different needs.