The turtle tank size calculator determines the minimum aquarium or enclosure size needed for your turtle based on species, shell length, and number of turtles. Proper tank size is critical for turtle health and longevity.
Calculate Turtle Tank Size
Turtle Tank Size Guidelines
The general rule for aquatic turtles is 10 gallons of water per inch of shell length. A 6-inch red-eared slider needs at minimum a 75-gallon tank, with 100+ gallons recommended for adult females (which grow to 10-12 inches).
Water Depth and Basking Area
Water depth should be at least 1.5× the shell length so the turtle can right itself if flipped. A dry basking platform is mandatory — turtles need UVB lighting and heat on the basking spot to metabolize calcium and regulate body temperature. Without proper basking areas, turtles develop metabolic bone disease.
Frequently Asked Questions
Is this turtle tank size calculator free?
Yes, completely free with no signup required.
How big of a tank does a red-eared slider need?
The standard rule for red-eared sliders (and most aquatic turtles) is 10 gallons per inch of shell length, with a minimum of 40 gallons for adults. A full-grown female red-eared slider (10-12 inches shell length) needs at least 100-120 gallons. Males are smaller (5-9 inches) and can do with 75-90 gallons. Bigger is always better.
What does an aquatic turtle tank need?
Aquatic turtles need: (1) Adequate water depth (at least 1.5x shell length), (2) A basking area where the turtle can completely leave the water and dry off, (3) UVB lighting over the basking area (10-12 hours/day), (4) Basking spot temperature of 90-95°F (32-35°C), (5) Water temperature of 72-78°F (22-25°C), (6) Powerful filtration (rated for 2x actual water volume due to turtle waste).
Can two turtles share a tank?
Two turtles can cohabitate if the tank is large enough and they are compatible sizes. A general rule: add 50% more space for each additional turtle. Two 6-inch turtles need 90 gallons minimum. However, two male red-eared sliders often fight — same-sex female pairs or male+female combinations are more commonly successful.
How often do I need to clean a turtle tank?
With adequate filtration (canister filter rated for 2x water volume), water changes of 25-50% every 2-4 weeks are typical. However, turtles produce significantly more waste than fish. Monitor water parameters (ammonia, nitrite, nitrate) weekly at first to find your specific maintenance schedule. Smell and water clarity are rough indicators but parameters can be poor before visible signs.