UVB Distance & Lighting Calculator

Get the right UVB bulb strength and mounting distance for your species. Based on Ferguson Zones and manufacturer specs.

Critical Care

Incorrect UVB is the #1 cause of metabolic bone disease (MBD) in captive reptiles. Too far and your reptile can't synthesize vitamin D3. Too close and you risk burns or photo-kerato-conjunctivitis. There's no margin for guessing here.

Your Setup

Species

Bulb Type

Mounting Position

Enclosure Height

Top to floor

Basking Spot Height

Floor to top of basking decor

Enclosure Length

Used to recommend the right tube length for the Light & Shade method.

Zone 3 — Bearded Dragon

17in

From the bulb to your reptile's back when basking. Delivers UVI 4–6, matching wild conditions for bearded dragons.

4–6

Target UVI at basking

18in

Your current distance

✓ On target

Setup status

Setup Specifications

Ferguson ZoneZone 3

Target Basking UVI4.0–6.0

Recommended Tube Length34 in (66% coverage)

Bulb ReplacementEvery 12 months

Mesh AttenuationNone — bulb inside

Photoperiod12–14 hr on / 10–12 off

View full Bearded Dragon species profile

Setup Notes for This Species

Tube length
Use a 34-inch tube to cover about 66% of your enclosure length. The remaining shaded area lets your reptile photoregulate naturally.
Replacement
Replace this bulb every 12 months. Mark your calendar with the install date — output drops well before the bulb stops lighting up.
Photoperiod
12–14 hours of UVB in summer, 10 in winter. Seasonal photoperiod variation reflects natural conditions.
Supplements
Use plain D3-free calcium dust for insectivores when proper UVB is provided. Reptiles synthesize their own D3 — adding more on top can cause overdose.
Verify output
For high-UVB species, consider a Solarmeter 6.5 to measure actual UVI at your basking spot.