Reptile Enclosure Heat & UVB Distance Estimator
Check basking temperature and UVB distance ranges
Reptile basking heat and UVB distance FAQ
What does this reptile enclosure calculator actually do?
This page combines a species preset, a generic UVB bulb type and your lamp-to-basking distance. It then shows a target basking temperature band in °F/°C and a rough UV Index estimate at that distance, plus an approximate distance window where many keepers aim to position that type of bulb.
Is it giving me exact basking temperatures for my reptile?
No. The tool only shows target ranges for the species preset, based on common veterinary husbandry guidance. Real basking surface temperature depends on your room temperature, bulb wattage, fixture, mesh lids, substrate and décor. Always confirm with a digital probe or infrared thermometer and adjust height, wattage or thermostat settings as needed.
How accurate is the UVB distance and UVI estimate?
UV output is calculated from a simple “typical” UVI at 12 in for each lamp type and then scaled by distance. It cannot see your exact brand, reflector, mesh or lamp age, so treat it as a ballpark only. The safest way to dial in UVB is with a Solarmeter-style UV Index meter and the manufacturer’s charts for your specific bulb.
Which species presets should I use for other reptiles?
The presets are grouped by basking style and habitat, not just species names. For example, many daytime desert baskers will be similar to the bearded dragon profile, while some nocturnal geckos fit better with the leopard gecko style band. If in doubt, pick the closest match and then cross-check with a species-specific care sheet from a trusted vet or herp group.
Why does the tool talk about UVI instead of “% UVB”?
Lamp packaging often uses numbers like 5.0, 10.0, 6%, 12%, but these do not tell you how much UVB actually reaches your reptile. The UV Index (UVI) is a standardised way to describe UV intensity at the basking spot, just like human weather forecasts. Many modern reptile lighting guides work in Ferguson-style UVI zones so keepers can build safe gradients instead of guessing from box labels.
Can I use this instead of a thermostat or UV meter?
No. The calculator is designed as a layout helper and sense-check, not a control system. Heat sources should always be used with suitable thermostats and temperature probes, and UVB levels should ideally be checked with a proper UVI meter and manufacturer data. Think of this page as something you use before you buy bulbs and while you refine your enclosure, not instead of monitoring.
What if my reptile has health problems or is recovering?
Sick, underweight or recovering reptiles often need tighter control of basking temperature and UV than healthy adults. In those cases, follow your reptile vet’s prescription even if it differs from a generic calculator. You can still use this tool to visualise the plan, but the vet’s instructions always win.
How to use this reptile heat & UVB distance estimator
The aim of this calculator is to turn three basic facts — your reptile species group, UVB bulb type and distance to the basking spot — into a simple summary of target basking temperatures and a rough UVI band at that perch.
1. Pick the nearest species preset
Start by choosing the preset that best matches your reptile’s natural lifestyle: a daytime desert basker (like a bearded dragon), a crepuscular ground-dweller (like a leopard gecko), a snake that thermoregulates along a gradient (such as a corn or king snake), a cooler, arboreal gecko, or a small Mediterranean tortoise. The preset sets a typical basking temperature range, a cooler end and a UVI target band at the main basking spot.
2. Choose distance units and UVB lamp type
The tool loads with inches (in) first for US keepers. If you measure in centimeters, switch the units box to cm and the label above the distance field updates to match. Then select the UVB bulb type that is closest to what you actually own — for example a T5 HO 5–6%/5.0 tube, a T5 HO 10–12%/10.0 tube, a T8 strip, a compact coil or a mercury vapor combo lamp.
3. Measure from the bulb to the basking surface
Using a tape measure, measure straight from the front of the UVB lamp (or the inside of the mesh right under it) down to the top of the basking rock, branch, hide or platform where your reptile sits to soak up heat and light. Enter that distance in the chosen unit. This is the key number the calculator uses to make its UVB distance and UVI estimate.
4. Read the basking temperature and UVB distance guidance
When you click Estimate heat & UVB band, the left side of the summary card shows:
- The target basking temperature range in °F with °C alongside.
- A typical cool end range for that species group.
- A short note reminding you to confirm with real thermometers.
The right side shows:
- Your entered distance in the chosen unit and in the other unit.
- A rough UVI estimate at that distance for the lamp type.
- A suggested distance window where many keepers aim to position that bulb for the preset’s UVI band.
- A short verdict such as “likely below range”, “roughly in band” or “likely high for long basking sessions”.
5. Use the copyable summary while you tune the enclosure
The Copy summary button creates a plain-text version of the plan you can paste into a notes app, email to your vet or keep next to your enclosure. As you add a thermostat, adjust wattage, move branches and check with a UV meter, you can update the numbers here and keep a clear record of how the habitat is changing over time.
Treat this tool as a starting point and safety check; the real work is watching your reptile, logging temperatures and UVI with proper instruments, and adjusting the environment until both the numbers and your pet’s behaviour sit comfortably in range.
How the basking temperature ranges & UVB distance math works
The internal math is intentionally simple and conservative. It blends published husbandry ranges for different reptile types with a basic inverse-square style UV model for common lamp types, then translates everything into the °F/°C and distance units you actually use around the tank.
1. Species presets and basking temperature targets
Each species preset stores a typical basking temperature range and a cool end range in °F, based on common veterinary and husbandry guidance for that style of reptile. The calculator also stores a simple UVI band at the basking spot that lines up with Ferguson-style UV exposure zones used in many modern lighting guides.
2. UVB lamp types and a rough UVI estimate
For each UVB bulb type, the tool assumes a “typical” UVI at 12 inches over a basking surface. It then treats the lamp as a simple point source and scales that output with the square of the distance:
Estimated UVI at distance d ≈ baseUVI × (12 ÷ d)2
This is not a substitute for real lamp tests and ignores mesh, reflectors and lamp ageing, but it gives a useful sense of whether a basking perch is likely to sit in very low, roughly in-band or very high territory for a given bulb type.
3. Suggesting a distance window for the chosen species
Using the species’ target UVI band and the lamp’s base output, the calculator solves for approximate distances at which the lower and upper band edges might occur. Those distances are rounded and clipped to a practical range (for example 4–36 in / 10–90 cm) to create a suggested distance window.
Your entered distance is then compared with that window and labelled as “likely below range”, “roughly in band” or “likely above range”, with reminders that only a UV meter can confirm real values.
4. Why you still need thermometers, thermostats and meters
Heat and light in a real vivarium are affected by room temperature, ventilation, substrate, hides, lamp age, mesh and fixtures. Even the best model cannot see those details, so the calculator is deliberately cautious: it tells you where many keepers start, not where you must end. Always combine it with:
- Digital thermometers or an IR temperature gun for basking and cool end temps.
- A suitable thermostat on heat sources to avoid burns and overheating.
- A UV Index meter and lamp manufacturer charts, especially for high-output bulbs.
Used together, these tools let you fine-tune a safe heat gradient and UVB gradient that match your individual reptile instead of relying on guesswork or marketing on a box.
References and further reading on reptile heat & UVB lighting
Use these resources alongside this estimator when planning or checking your reptile’s enclosure:
- MSD Veterinary Manual — Management and Husbandry of Reptiles — overview of temperature gradients, basking spots and lighting needs for many reptile groups.
- Baines et al. — How much UV-B does my reptile need? The UV-Tool — open-access paper introducing Ferguson-style UV zones and evidence-based UVB ranges.
- Royal Veterinary College — Reptile Heating & Lighting Guide (PDF) — concise vet-written factsheet on bulb choices, distances and safety.
- Lafeber Vet — UVB Lighting for Reptiles (PDF) — up-to-date, practical guide to UVB lamps, UVI measurement and safe gradients.
Whenever your reptile is sick, not eating, or behaving oddly, use this page as a conversation starter with a qualified reptile vet, not as a replacement for in-person care.