A UVB lamp loses ultraviolet output long before it stops lighting up, so whether the bulb still glows tells you nothing about when to replace it. Enter the rated UVB hours printed on the lamp, the hours it runs each day, the date it went into service and a reference date, and this tool gives the hours run, the share of rated life used, the days left and the replacement date.
The math is hours run = days elapsed x daily hours and replacement date = service date + roundup(rated life / daily hours). Rated life varies widely between products and lamp technologies, and there is no officially established figure, so this tool supplies none and asks for the one from your lamp or its maker (as of October 2026).
This tool does not measure actual UVB strength and does not recommend a UV index or a mounting distance. It assumes the daily run time never changes, so altering a timer shifts the result. This tool is for reference only and does not replace veterinary care. Contact a veterinarian who treats reptiles right away if your animal limps or its jaw feels soft, which can point to metabolic bone disease.
Frequently Asked Questions
Use the UVB life printed on the lamp packaging or given by the maker. There is no official standard, so this tool does not supply a figure.
No. Visible light can remain while UVB output has already dropped. Go by the rated hours, or confirm with a UV index meter.
Days left are rounded down and the replacement date is rounded up, so they can differ by one day. Days left counts the full days of use remaining, while the replacement date is the day the rated hours run out, usually one day after the last full day.