What does rated lamp life actually mean?

It is a decay specification: the hours at which output falls to a stated fraction of new, commonly 70 to 80%. A lamp at rated life still strikes; it just emits less, and whether that is enough is measurable.

Should I swap on hours or on a reading?

On a reading wherever you can take one. Hours predict decay loosely, and cycling, cooling and power setting all move it. A monthly reading shows what the hour meter is guessing at.

Why is the order date the headline?

Because the order date is a decision you can act on today. A lamp reaching its swap point with no spare leaves two bad options: run past the safe point or stop the line.

Does idle time consume lamp life?

On a mercury system, yes. The lamp is struck and aging whenever it is on, shuttered or not. UV LED switches instantly, so it ages only while curing.

UV Curing calculator

UV Lamp Life Calculator

Turn rated lamp hours into a planned swap date and, from the spare's lead time, the day the order must be placed. Enter hours remaining, daily runtime, the safety factor and lead time.

What this calculator does

Convert rated lamp hours and daily runtime into a swap date, and from the lead time the order date.

Formula used

Days to rated end = rated hours remaining ÷ daily runtime
Days to planned swap = days to rated end ÷ safety factor
Days to place the order = days to swap − lead time
Rated hours given up = remaining − remaining ÷ safety factor
A negative order date means the order is already late

Inputs explained

Rated Lamp Life Remaining: Rated hours minus hours run, from the hour meter.
Average Daily Lamp Runtime: Hours the lamp is struck per day, averaged.
Replacement Safety Factor: How much of rated life you decline to use.
Replacement Lamp Lead Time: Order to on-shelf, including purchasing time.

How to use the result

Best suited to setting a lamp reorder point, planning lamp changes into a shutdown, justifying a shelf spare for a long-lead lamp.
Hours poorly predict output; cycling, cooling and power setting all move decay. Does not tell you whether the lamp delivers the required dose today; that needs a radiometer. Cannot see premature failures such as seal leaks or a cracked sleeve.

Common questions

What does rated lamp life actually mean? It is a decay specification: the hours at which output falls to a stated fraction of new, commonly 70 to 80%. A lamp at rated life still strikes; it just emits less, and whether that is enough is measurable.
Should I swap on hours or on a reading? On a reading wherever you can take one. Hours predict decay loosely, and cycling, cooling and power setting all move it. A monthly reading shows what the hour meter is guessing at.
Why is the order date the headline? Because the order date is a decision you can act on today. A lamp reaching its swap point with no spare leaves two bad options: run past the safe point or stop the line.
Does idle time consume lamp life? On a mercury system, yes. The lamp is struck and aging whenever it is on, shuttered or not. UV LED switches instantly, so it ages only while curing.

Last reviewed 2026-10-01.