# Reptile UVB calculator

> Set your species, bulb type, wattage, and current mounting distance to estimate the recommended bulb-to-basking distance and expected UV index. Results are estimates from published reference values — confirm them with a Solarmeter 6.5.

## Recommended setup

Use the interactive calculator on the page: https://petguidecalc-dev.pages.dev/reptile/uvb-calculator/ — select a species, bulb type, wattage, and distance to get a distance range and expected UV index.

## Species UVB requirements

| Species | Ferguson zone | Target basking UVI | UVB need |
|---|---|---|---|
| Bearded dragon | Zone 3 — open basking | 3.0–6.0 | required |
| Leopard gecko | Zone 1 — shade | 0.5–1.5 | recommended |
| Crested gecko | Zone 1 — shade | 1.0–2.0 | recommended |
| Ball python | Zone 1 — shade | 0.5–1.5 | optional |
| Corn snake | Zone 2 — occasional basking | 1.0–2.0 | recommended |
| Uromastyx | Zone 4 — partial sun | 4.0–6.0 | required |

## How the estimate is calculated

Each species has a published target UV index range for the basking spot, derived from Ferguson-zone exposure guides and species care references (ReptiFiles, Arcadia, veterinary sources).

Each bulb type is mapped to a typical UV index at 30 cm (12 in) — measured values from published product tests with a reflector and no mesh. The calculator applies the inverse-square law to estimate the distance range that keeps the basking spot inside the species target range.

Wattage is used as a proxy for output class (for example, a 39 W T5 HO is treated as a 10% tube). Verify your actual tube concentration and measure the real UV index with a Solarmeter 6.5.

## Frequently asked questions

**Q: What UV index does a bearded dragon need?**

A basking spot UV index of roughly 3.0–6.0, which typically means a T5 HO 10–12% bulb mounted about 26–44 cm (10–17 in) above the basking surface without mesh. Verify with a Solarmeter 6.5.

**Q: Do ball pythons need UVB?**

UVB is optional for ball pythons, but low-level output (2.5–6% T5 HO, such as an Arcadia ShadeDweller) supports natural behaviour. A 12% high-output tube is too strong for this species.

**Q: Can I use a compact fluorescent UVB bulb?**

Compact bulbs work for low-UV species when mounted close, but their beam is narrow and output falls off sharply with distance. They are not recommended as the main UVB source for basking lizards.

**Q: Does a mesh top reduce UVB?**

Yes. Mesh screens typically block 30–50% of UVB. Mount the bulb accordingly and always confirm the result with a UV index meter.

**Q: How often should I replace a UVB tube?**

T5 HO tubes should be replaced about every 12 months. Output drops gradually even while the tube still looks bright; an annual replacement keeps the dose predictable.

_Estimate values are from published references; verify with a Solarmeter 6.5. PetGuideCalc — https://petguidecalc-dev.pages.dev_