Basking, ambient and night temperatures for your species, the gradient you need to build between them, and an honest answer about wattage — which is that no formula exists and a temperature gun settles it.
Last reviewed August 2026 · Free · Nothing you enter is stored
A reptile does not produce its own body heat. It regulates temperature by choosing where to sit, moving into warmth to raise its body temperature and into shade to lower it, and it does this continuously through the day in response to what it is doing — digesting a meal, fighting an infection, or simply resting.
That behaviour only works if the enclosure gives it something to choose between. An enclosure held at one uniform temperature, however carefully that temperature was picked, takes the decision away from the animal entirely. Digestion slows or stalls at the wrong temperature, and immune response depends on the animal being able to raise its temperature when it needs to. Neither is something the keeper can supply by picking a better single number.
So the target is not a temperature, it is a range across the enclosure: a hot basking site at one end, a warm ambient area around it, and a genuinely cool end far enough away to stay cool. This is another argument for enclosure size, and a practical one. Three feet of length is not much room in which to drop thirty degrees, and the shorter the enclosure the more the two ends bleed into each other. Our enclosure size calculator covers the footprint side of the same problem.
Every species in our data, with the basking surface temperature, both ambient ranges, the night-time range and the humidity target. Any of these can be selected in the dropdown above.
| Species | Basking surface | Warm ambient | Cool ambient | Night | Humidity |
|---|---|---|---|---|---|
| Bearded Dragon | 108–113°F | 85–99°F | 77–85°F | 55–75°F | 30–40% |
| Leopard Gecko | 94–97°F | 85–90°F | 70–77°F | 60–72°F | 30–40% |
| Crested Gecko | 82–85°F | 78–85°F | 70–75°F | 65–72°F | 60–80% |
| Gargoyle Gecko | 82–84°F | 77–84°F | 72–74°F | 68–77°F | 50–70% |
| Ball Python | 86–90°F | 86–90°F | 72–80°F | 70–78°F | 60–80% |
| Corn Snake | 88–90°F | 85–90°F | 75–82°F | 70–78°F | 65–75% |
| Kingsnake / Milk Snake | 85–90°F | 85–90°F | 70–78°F | 68–75°F | 40–60% |
| Blue-Tongue Skink | 100–105°F | 80–90°F | 70–80°F | 65–75°F | 40–60% |
| Green Anole | 88–90°F | 80–88°F | 70–77°F | 65–75°F | 60–70% |
| Veiled Chameleon | 83–88°F | 75–82°F | 72–78°F | 55–65°F | 40–50% |
| Panther Chameleon | 85–90°F | 75–82°F | 72–77°F | 60–70°F | 50–60% |
| Red-Eared Slider | 95–104°F | 85–90°F | 75–85°F | 70–80°F | Aquatic — n/a |
| Ornate Box Turtle | 90–95°F | 80–90°F | 70–77°F | 65–75°F | 30–60% |
| Russian Tortoise | 93–97°F | 75–85°F | 70–80°F | 65–75°F | 40–60% |
| Hermann's Tortoise | 95–100°F | 75–85°F | 68–78°F | 60–72°F | 50–70% |
| Sulcata Tortoise | 100–105°F | 80–90°F | 75–85°F | 70–75°F | 50–80% |
Temperature, humidity and enclosure figures follow ReptiFiles, the most consistently evidence-informed husbandry reference in the hobby, cross-checked against veterinary sources. None of it comes from controlled research — captive husbandry parameters are derived from field climate data and keeper consensus, and the honest framing is 'best available guidance' rather than 'proven'. Ferguson zone assignments follow Baines et al. (2016). The 'commonly sold' enclosure column records what starter kits and pet shops actually supply, which is frequently far below the recommended minimum.
People arrive at this question expecting something like the aquarium heater rule, where watts per gallon gets you close enough. No equivalent exists for reptiles, no manufacturer publishes one, and the reason is that too many variables move at once.
Room temperature sets the baseline the lamp is working up from, and a 65°F basement and a 78°F living room are different problems. Enclosure material matters, because a wooden vivarium holds heat that a screen cage loses immediately. Ventilation changes how fast that heat leaves. Fixture design changes how the output is focused — a dome with a reflector concentrates heat that a bare socket scatters. And lamp height changes the delivered temperature roughly as an inverse square, so two inches of difference is not a small adjustment.
The method that actually works is to fit a lamp, let it run for an hour so the enclosure reaches equilibrium rather than measuring while it is still climbing, point an infrared temperature gun at the basking surface, and then adjust. If it reads too cool, lower the lamp or go up a wattage. Too hot, raise it or go down. This takes an afternoon and it produces an answer specific to your room, your enclosure and your fixture, which no formula could have done.
| Enclosure size | Starting wattage to try first |
|---|---|
| Up to 20 gallons / 24 x 18 x 18 | 50-75 W |
| 36 x 18 x 18 | 75-100 W |
| 48 x 24 x 24 | 100-150 W |
| 72 x 24 x 24 | 150 W, often two fixtures |
There is no published formula for reptile heating wattage, and no manufacturer offers one, because the answer depends on room temperature, enclosure material, ventilation, fixture design and lamp height all at once. These are starting points. The actual method is to fit the lamp, measure the basking surface with an infrared temperature gun, and adjust wattage or height until it reads right — always on a thermostat or dimmer.
The single most common measurement error is reading a stick-on dial thermometer on the side of the enclosure and treating that as the basking temperature. It is not. It is the temperature of the glass at that spot, which sits several inches from the basking site, often in a different plane relative to the lamp, and those dials are commonly out by ten degrees or more in their own right.
Point an infrared temperature gun at the surface the animal will actually lie on — the branch, the flat rock, the basking platform — and read that. It costs about twenty dollars and it is the difference between knowing your basking spot and assuming it. A digital probe placed directly on the basking surface is a reasonable second choice. Where the animal's back sits when it basks is the point being measured, so a branch that puts it four inches nearer the lamp changes the answer.
Two thermometers are better than one, placed at the warm end and the cool end, because the gradient is what you are trying to verify and a single reading cannot show it.
Heat rocks cause serious burns. Reptiles do not reliably move away from a surface hot enough to damage them, and thermal injury can take days to become visible, by which point the animal has been sitting on it repeatedly. The failure is not that the rock gets hot; it is that the animal stays on it. Belly-side heat sensing in reptiles is poor, the animal is seeking warmth, and it will keep seeking it on a surface that is already damaging tissue. There is no version of a heat rock that solves this, and the correct replacement is an overhead lamp or a thermostatted under-tank heater.
Under-tank heaters and ceramic heat emitters have no built-in cutoff and must run on a thermostat, not a timer and not unregulated. A thermometer tells you the temperature; a thermostat is what actually prevents a runaway. A timer is not a substitute, because a timer switches on the clock and has no idea what the temperature is doing — an under-tank heater on a timer will run flat out for its scheduled hours whatever the enclosure is reading. Buy the thermostat with the heat source, not later.
Many species benefit from a night-time temperature drop. Wild nights are cooler than wild days nearly everywhere, and the drop is part of the normal cycle rather than a fault to correct — the panther chameleon in this data specifically wants a cooler night with higher humidity than the day. The night range in the table is the floor to stay above.
If supplemental night heat is needed, it must not produce light. Coloured night bulbs, including the red and blue ones sold for the purpose, still emit visible light and disrupt the animal's day and night cycle. A ceramic heat emitter or a deep heat projector produces heat with no light at all, and either belongs on a thermostat.
The opposite problem is a room already warmer than the species' cool end should be, which is common with crested and gargoyle geckos in summer — they are among the few reptiles that can overheat at ordinary room temperature. Cooling an enclosure is much harder than heating one. The realistic options are to cool the room itself, move the enclosure to the coolest part of the house away from windows and heat sources, and use a larger enclosure so the cool end has room to sit further from the heat source. Increasing airflow and misting help at the margin. Frozen bottles and similar improvisations produce swings rather than a stable cool end, and are not a solution.
There is no formula, and no manufacturer publishes one, because room temperature, enclosure material, ventilation, fixture design and how high the lamp sits all move the answer at once. Two identical enclosures in two different rooms need different bulbs. The starting points in the table here get you to roughly the right shelf in the shop; the actual method is to fit the lamp, let it stabilise for an hour, measure the basking surface with an infrared temperature gun, and then change wattage or lamp height until it reads right. Anyone who gives you a watts-per-gallon number is guessing.
A reptile does not generate its own body heat, so it regulates temperature by moving — into the sun to digest and raise immune activity, into shade to cool down. That only works if the enclosure offers a genuine range from one end to the other. An enclosure held at a single temperature, however carefully chosen, removes the animal's ability to make that decision at all, and digestion and immune function suffer for it. This is also one of the strongest arguments for a larger enclosure: a short enclosure physically cannot hold a wide gradient.
No. Heat rocks cause serious burns, and the mechanism is what makes them dangerous rather than the temperature alone. Reptiles do not reliably move away from a surface hot enough to damage them, because their belly-side heat sensing is poor and the animal is seeking warmth. Thermal injury can take days to become visible, so by the time the damage shows the animal has been sitting on it repeatedly. Use an overhead lamp or a thermostatted under-tank heater instead.
Yes, and for an under-tank heater as well. Neither device has a built-in cutoff — plugged straight into the wall they will keep heating for as long as they have power, with nothing to stop the surface running away. A timer does not fix this either, since it switches on the clock and knows nothing about temperature. A thermometer tells you what the temperature is; a thermostat is what prevents the runaway. This is the single cheapest piece of equipment that prevents a serious injury.
With an infrared temperature gun pointed at the basking surface itself — the branch, rock or platform where the animal's body will actually sit. A stick-on dial thermometer on the side of the glass measures the glass, several inches away from the basking site and often in the wrong plane entirely, and those dials are frequently out by ten degrees or more regardless. A digital probe placed on the basking surface is an acceptable second choice; the dial stuck to the wall is not a measurement.
Many species benefit from one, and several of the chameleons in this data need it. Wild nights are cooler than wild days almost everywhere, and a modest drop is normal rather than something to be prevented. Two rules apply. A bright light at night is not acceptable — coloured night bulbs still emit visible light and disrupt the animal's day-night cycle, so if supplemental night heat is needed it should come from a ceramic heat emitter or a deep heat projector, both of which produce no light. And the drop must stay above the species' night floor, which is in the table above for every species here.
