Terrarium Heat Gradient Calculator
Calculate basking and cool end temperatures for any terrarium.
Enter warm side target and enclosure length to plan the full heat gradient for reptiles.
Terrarium Heat Gradient Planning
Reptiles are ectotherms — they regulate body temperature by moving between warm and cool zones. A proper heat gradient is the most important factor in reptile health.
Why a gradient matters: Without a gradient, reptiles cannot thermoregulate. A single warm temperature forces the animal to overheat or avoid heat entirely. A gradient lets the animal choose its own body temperature throughout the day.
Recommended gradients by species type:
| Species Group | Basking Spot | Warm Side | Cool Side |
|---|---|---|---|
| Desert lizards (bearded dragon, uromastyx) | 100-110F (38-43C) | 85-95F (29-35C) | 75-80F (24-27C) |
| Tropical lizards (water dragon, anole) | 90-95F (32-35C) | 80-85F (27-29C) | 72-78F (22-26C) |
| Snakes (corn, ball python) | 88-92F (31-33C) | 80-85F (27-29C) | 72-76F (22-24C) |
| Tortoises | 95-105F (35-40C) | 85-90F (29-32C) | 75-80F (24-27C) |
| Amphibians | No basking needed | 72-78F (22-26C) | 65-72F (18-22C) |
The 1/3 rule: The basking zone should occupy roughly 1/3 of the enclosure floor space. The remaining 2/3 should grade from warm-ambient to cool ambient. This gives the animal meaningful choice without wasted space.
Equipment for maintaining gradient:
- Basking spot: incandescent or halogen spot bulb (not ceramic heat emitter)
- Warm ambient: under-tank heater on a thermostat (snakes) or low-watt bulb (lizards)
- Cool side: no heating element — room temperature is usually sufficient
- Thermostat: always use a thermostat to prevent overheating
- Thermometers: two digital probes — one on each side, measured at ground level
Night drops: Most species benefit from a 10-15F night drop. This mimics natural desert / tropical temperature cycles. Turn off basking lights at night; ceramic heat emitters or red night bulbs maintain minimum temps.