Turtle Tank Calculator
Aquatic turtle planning only • species and swimming ability matter.
Turtle & Tank Inputs
Water Volume & Equipment
Planning referenceWater volume, not full tank capacity.
Visual Tank & Basking Area
Illustrative layout • verify species-specific lighting, escape clearance and access. Not to physical scale.
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Calculated turnover • distinct from rated tank capacity.
Rated capacity and flow are different. Use effective filtration, water testing and routine maintenance.
Slider reference: about 90°F / 32°C at the basking area. Verify species guidance; follow lamp placement instructions.
Formula & Worked Example
Water target = shell length (in) × 10 US gal
Modeled water = length × width × water depth
1 US gal = 3.785411784 L
Frequently Asked Questions
Is 60 gal the water volume or tank size?
It is the shell-length water reference for one 6-inch aquatic turtle, not the aquarium’s brim-full capacity. Actual swimming water depends on the internal footprint and fill depth, with displacement subtracted in a real setup. The modeled example ignores displacement.
Does a bigger tank make cohabitation safe?
No. The +50% per additional turtle is a shared-space planning heuristic for similar-sized turtles, not a compatibility or welfare assessment. Aggression, competition, feeding and access to basking sites must be assessed separately; separate housing may be necessary. See ReptiFiles shared-housing guidance.
Is filter rated capacity the same as GPH?
No. Rated tank capacity is a manufacturer’s aquarium-size rating, expressed in gallons or litres. GPH/L/h is flow per hour. This tool displays a 2–3× water-volume rating reference separately from flow calculated at your entered turnover. Installed flow can be lower than advertised flow because of hoses, lift and media. Check real installed flow and water quality; even a powerful filter does not replace water changes. Calculations use unrounded intermediate values.
More turtle setup questions
What does the Turtle Tank calculator calculate?
A shell-length water target, geometric fill volume and full internal tank capacity, depth reference, dry-platform area, filter capacity reference and flow at a chosen hourly turnover. These are planning numbers, not a guarantee of safe or complete husbandry.
Which values should I enter?
Enter the largest straight shell length, a whole-number turtle count, and internal tank length/width/height. Enter fill depth below tank height, above-water dry-platform percentage of footprint and a positive hourly turnover assumption. Different-sized or weak-swimming species need individualized guidance.
What formula does this calculator use?
Target gallons = shell length in inches × 10 ×[1+0.5×(count−1)]. Modeled litres = length(cm)×width(cm)×depth(cm)/1000. Full capacity uses height instead of depth. Dry platform area = footprint × percentage/100. This is a linear extra-volume model, not repeated 1.5multiplication.
Why might my result differ from another source?
Different care sources use different reference volumes and welfare assumptions. Real tanks have wall thickness, substrate, decor, structures and displacement, while these calculations use internal empty-water geometry. Rated full tank volume is not equal to usable swimming water.
Does the result update automatically?
Yes. All inputs and unit choices update the results and schematic. Presets set illustrative shell length/count/fill-depth examples: Slider 6 in, 1 turtle, 12.5 in fill; Juvenile 3 in, 1 turtle, 6.5 in fill; Multiple 6 in, 2 turtles, 12.5 in fill. Tank dimensions are retained, so the existing setup can be compared with a changed target.
What is the rule for turtle tank size?
A 10 US-gallons-per-inch-of-shell-length guideline is one reference for capable swimming aquatic turtles, such as sliders. It is not a universal rule for every turtle or every life stage. VCA discusses 10 gallons/inch and 1.5–2×shell-length depth references; species-specific care and adult growth still matter.
Do box turtles need the same aquarium?
No. This tool is for aquatic turtle water planning. Terrestrial box turtles and tortoises need different enclosures and species-specific husbandry; the aquatic formula should not be applied to them. Plan for adult growth; this tool does not assess behavior, injury risk or escape protection.
Is the displayed depth a maximum safe depth?
No. The 1.5–2×shell-length depth band is a general reference, not a maximum or an individualized safety determination. The entered fill depth controls modeled volume. The aquarium photograph is illustrative, is not a lamp installation plan, and its animal illustrations are not an animal-count diagram. Hatchlings, weak swimmers and unwell turtles need appropriate resting areas, access and individualized depth advice.
Does the platform reduce the modeled water volume?
The model assumes an above-water platform and therefore does not subtract a percentage of water volume. All entered dimensions are internal. Real supports, ramps, submerged structures and other decor displace water; account for them before deciding how much usable water is provided.
Are the example temperatures universal?
No. The about 32°C/90°F basking reference is from terrapin guidance. Water temperatures, thermogradients, UVB intensity and lamp distance depend on species, life stage and equipment. Measure actual temperatures and follow verified species and lamp guidance.
What does the adequacy message mean?
It compares geometric modeled water with the shell-length target only. A result at or above target does not verify footprint suitability, adult housing, access, filtration performance, compatibility or animal health. Tank fill depth must remain below total internal height, but this alone does not verify escape protection.
Helpful Sources
Turtle Tank Calculator Calculate the minimum recommended aquarium size for a pet turtle based on shell length. — free online calculator.