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Bearded Dragon Tank Size Calculator — By Age & Length

What size tank does your bearded dragon need at each life stage? This calculator sizes the enclosure for all four growth phases — baby (0-6 mo), juvenile (6-12 mo), sub-adult (12-18 mo), and adult (18+ mo) — using ARAV welfare standards and experienced-keeper consensus from Association of Reptilian & Amphibian Veterinarians resources. Adults need a 75+ gallon tank (48 × 24 × 24 in minimum) with proper UVB, basking spot, and thermal gradient.

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Life stage
Sub-adult
Age: 6–12 mo · Length: 16–20 in
Minimum
55 gal
Recommended
75 gal
Ideal
120 gal

Suggested enclosure

48″ × 24″ × 24″

Beardies need length more than height — PVC reptile enclosures (Dubia, Animal Plastics) provide better thermal gradient than aquariums. Basking spot 100-110 °F, cool side 75-85 °F.

Bearded dragon tank size by life stage

Life stageAgeBody lengthMin tankRecommended
Baby0-3 mo4-11 in20 gal long (30×12×12)40 gal (36×18×18)
Juvenile3-6 mo11-16 in40 gal (36×18×18)75 gal (48×18×21)
Sub-adult6-12 mo16-20 in75 gal (48×18×21)120 gal (48×24×24)
Adult12+ mo18-24 in75 gal (48×18×21)120-180 gal (48-72 × 24 × 24)

Glass aquarium dimensions in inches. Length matters more than height — beardies are terrestrial, not arboreal.

Bearded dragon husbandry terminology

Thermal gradient
Temperature range across the enclosure — 95-110 °F basking, 75-85 °F cool end; lets the dragon thermoregulate.
UVB output (T5 HO)
Ultraviolet-B lighting needed for vitamin D₃ synthesis and calcium absorption — Arcadia 12% or ReptiSun 10.0 T5 standard.
MBD (metabolic bone disease)
Calcium / D₃ deficiency causing soft, deformed bones — the #1 preventable disease in pet beardies.
Brumation
Reptile equivalent of hibernation; reduced activity and feeding during cooler months in mature adults.

Frequently Asked Questions

What size tank does a bearded dragon need?

Adult bearded dragons need a minimum 75 gallon tank (48"×24"×24"); 120+ gallon (72"×24"×24") is ideal. Babies can start in 20-40 gallons but upgrade by 6 months. Length and floor space matter more than height.

Can a bearded dragon live in a 40 gallon tank?

40 gallons (36"×18"×18") is fine for juveniles up to 6 months but becomes cramped for adults. A 75-120 gallon is needed by 12 months.

Do bearded dragons need a screen lid?

Yes, for glass tanks — for airflow and to hold lights. For PVC enclosures with built-in ventilation panels, no lid is needed. Screens reduce UVB by 30-50 %; reduce bulb distance accordingly.

Why is a bigger tank better?

Beardies are active and need a proper thermal gradient (basking 105-110 °F to cool 75-80 °F). Undersized tanks can't establish this gradient, causing chronic stress, metabolic bone disease and impaction.

Can two bearded dragons live together?

No. Beardies are solitary and territorial. Co-housing causes stress, fighting, parasites and suppressed growth in the subordinate. Even 'bonded' pairs observed on YouTube often show stress signs.

Sources & References

  1. [1]
    ARAV Bearded Dragon Care Guide — Association of Reptilian and Amphibian Veterinarians
  2. [2]
    BeardedDragon.org Husbandry — BeardedDragon.org community
  3. [3]

Common mistakes to avoid

  • 20-gallon tank for an adult — 40 gallon breeder is the minimum for adults. 75+ gallon preferred.
  • Sand substrate for juveniles — high impaction risk. Use reptile carpet or tile until 12+ months.
  • CFL coil UVB bulb — inadequate UVB output; associated with eye damage. T5 HO linear UVB only.

When to call the vet immediately

  • Soft jaw, tremors, twitching limbs — MBD. Immediate vet visit + correct husbandry.
  • Black beard displayed constantly — stress (cage too small, wrong temperatures, visible predators).

Pro tips

  • Basking surface temp: 95-105°F (juveniles 100-110°F). Measure with a temp gun, not an ambient probe.
  • Cool side: 75-85°F. Night drop to 65-75°F OK if the dragon is healthy.
  • Humidity: 30-40% in most US homes. Too-high humidity causes respiratory infection.