An adult bearded dragon needs a tank of at least 4×2×2 ft (48×24×24 in, about 120 gallons), and 6×2×2 ft (about 180 gallons) is better. Buy the adult size from the start, even for a baby. A dragon reaches adult size at around 10 months, so a starter tank is outgrown within the year. Measure tanks by length, depth and height, not by gallons.
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Bearded dragon tank size by age
| Age | Tank size | Notes |
|---|---|---|
| Baby (0–3 months) | 4×2×2 ft, the adult size | Zen Habitats recommends starting babies in their adult enclosure rather than buying several. |
| Juvenile (3–10 months) | 4×2×2 ft or larger | A dragon kept in a small tank will need upgrading in as little as 6–8 months (Zen Habitats). |
| Adult (10 months on) | 6×2×2 ft recommended; 4×2×2 ft minimum | ReptiFiles accepts 4×2×2 ft only for small adults under about 18 in. |
Zen Habitats puts adult size at around 10 months. ReptiFiles cites an average adult length of 19–23 in, and the RSPCA says adults grow to around 45 cm (18 in) including the tail. Weigh and measure your own dragon rather than going by age.
Tank sizes in gallons and feet
Gallons describe the volume of a glass aquarium, not the shape. Two tanks of the same gallons can have very different floor space, and floor space is what a bearded dragon uses. This table converts the common sizes.
| Sold as | Dimensions (L×D×H) | Verdict for one adult |
|---|---|---|
| 20 gallon long | 30×12×12 in | Too small at any age past the first weeks |
| 40 gallon breeder | 36×18×16 in | Too small. Zen Habitats calls it inadequate for adults. |
| 75 gallon aquarium | 48×18×21 in | Below the minimum: too narrow and too short |
| 120 gallon (4×2×2 ft) | 48×24×24 in | The minimum |
| 180 gallon (6×2×2 ft) | 72×24×24 in | Recommended by ReptiFiles |
| 240 gallon (8×2×2 ft) | 96×24×24 in | Ideal if you have the space |
Aquarium dimensions vary slightly by brand. A 4×2×2 ft box works out to about 120 US gallons (48×24×24 in divided by 231 cubic inches per gallon), which is where the “120 gallon” name comes from. In the UK the same box is sold as a 4ft vivarium, 120×60×60 cm, which the RSPCA sets as the minimum for one adult.
What the main care sources say
| Source | Adult minimum | Babies and juveniles |
|---|---|---|
| ReptiFiles | 6×2×2 ft (24 cubic ft); 4×2×2 ft for adults under about 18 in | No separate size given |
| Zen Habitats | 4×2×2 ft, about 120 gallons | Start in the adult enclosure |
| RSPCA | 120×60×60 cm | No separate size given |
| VCA Animal Hospitals | 60–100 gallons or larger as the dragon grows; length at least 3 times the dragon’s total length | 20 gallons minimum for a juvenile |
VCA’s figures are the smallest of the four. We follow the larger sources, because a 4ft enclosure is the shortest that holds a basking spot and a cool end far enough apart. Our heat lamp guide has the temperatures each end needs.
Tanks we would buy
- Best overall: Zen Habitats 4×2×2 ft PVC enclosure. The minimum size in PVC, which holds heat better than glass, with front doors and a substrate shield.
- Best upgrade: Zen Habitats 6×2×2 ft enclosure. The size ReptiFiles recommends. Buy this if you have the floor space.
- Best lockable: Zoo Med ReptiHabitat PRO 120. A 4×2×2 ft PVC enclosure with glass doors that latch shut.
- Best glass: REPTIZOO 120 gallon glass terrarium. Front-opening glass for display. It loses heat faster than PVC, so check your temperatures in a cool room.
Our 120 gallon enclosure picks compare these models in detail.
Can a baby bearded dragon live in a big tank?
Yes. Some keepers worry that a baby will struggle to find food in a large tank. Feeding in a shallow dish or by hand solves that. Zen Habitats recommends the adult enclosure from the start. Set it up as you would for an adult: a full-length UVB tube, a basking spot at one end, and plenty of cover so a small dragon feels safe. See the UVB light guide for tube length and distance.
How tall should the tank be?
At least 2 ft (24 in, 60 cm). ReptiFiles recommends 3 ft of usable height where possible, because bearded dragons climb. Height also keeps the basking lamp and UVB tube far enough above the basking platform once you add 4–6 in of substrate.
Tank size for two bearded dragons
Keep one dragon per tank. ReptiFiles strongly recommends against housing bearded dragons together under any circumstances, and the RSPCA and VCA both say they are best housed alone. Two males fight, a male and female will breed, and an adult can injure or eat a smaller dragon. A bigger tank does not fix this, so plan on two separate enclosures.
Common mistakes
- Buying a small starter tank. A 20 or 40 gallon tank is outgrown within months.
- Going by gallons. A 75 gallon aquarium sounds big but is only 18 in deep.
- Top-opening tanks. Reaching in from above stresses a bearded dragon. Pick front-opening doors.
- Upgrading in stages. Buying a 40, then a 75, then a 4×2×2 costs more than buying the adult size once.
Once you have the tank, our enclosure setup guide covers the layout, and the care guide covers daily routine.
FAQ
What size tank does a bearded dragon need?
At least 4×2×2 ft (48×24×24 in, about 120 gallons) for one adult. ReptiFiles recommends 6×2×2 ft (about 180 gallons).
Is a 40 gallon tank big enough for a bearded dragon?
No. A 40 gallon breeder is about 36×18×16 in, which is too small for an adult. Zen Habitats calls 40 gallon breeders inadequate for adult bearded dragons.
Is a 75 gallon tank big enough for a bearded dragon?
No. A 75 gallon aquarium is 48 in long but only about 18 in deep, which is below the 4×2×2 ft minimum.
What size tank does a baby bearded dragon need?
The adult size, 4×2×2 ft or larger. Bearded dragons reach adult size at around 10 months, so a small tank is outgrown quickly.
How big is a 120 gallon tank in feet?
4 ft long, 2 ft deep and 2 ft tall (48×24×24 in, or 120×60×60 cm).
Can two bearded dragons share a tank?
No. ReptiFiles strongly recommends against housing bearded dragons together, and the RSPCA and VCA say they are best housed alone. Use separate enclosures.
Sources
- ReptiFiles: bearded dragon terrarium size
- Zen Habitats: what size enclosure do bearded dragons need
- RSPCA: bearded dragon care
- VCA Animal Hospitals: bearded dragons, housing
More guides: enclosure size and setup, 120 gallon enclosures, UVB light, heat lamp, care.