How do you calculate UV dwell time under a lamp?

Convert the cure-zone length to feet, divide by belt speed in ft/min, then multiply by 60 to get seconds. A 10-inch zone at 30 ft/min gives a base dwell of 0.33 seconds before any safety margin.

What is a good UV dwell time?

There is no universal number — it depends on the coating's required dose and the lamp's irradiance. The goal is enough dwell to hit the dose spec at your line speed; the calculator's margin (20% in the example) builds in headroom for lamp aging and speed drift.

Why add a dwell margin?

Lamps lose output as they age, belt speeds drift, and radiometers have tolerance. A 20% margin — turning a 0.33 second base dwell into 0.40 seconds — protects against under-cure as conditions degrade between maintenance intervals.

How does belt speed affect UV cure?

Dwell is inversely proportional to belt speed, so doubling the speed halves the exposure time and the delivered dose. Speed is the single biggest lever on cure, which is why it should be set from the dose requirement, not from throughput targets alone.

How do I convert required UV dose into a belt speed?

Divide the required dose by the lamp's irradiance to get the needed dwell in seconds, then rearrange this formula to solve for belt speed given your cure-zone length. This calculator lets you check the resulting dwell has enough margin.

Dwell time vs UV dose — what's the difference?

Dwell is exposure time in seconds; dose (mJ/cm²) is irradiance multiplied by dwell. Two lines with identical dwell can deliver very different doses if their lamps output different irradiance, so always confirm both.

UV Curing calculator

UV Dwell Time Calculator

UV dwell time is how long any single point on a part stays inside the lamp's cure zone as the conveyor carries it through. It is set by the length of the illuminated zone and the belt speed, with a margin added for process safety. Line engineers use it to confirm the coating gets enough exposure to reach full cure, and to translate a supplier's required dose into a maximum belt speed. Too short a dwell and the coating leaves the lamp under-cured; too long and you are throttling throughput for no gain.

What this calculator does

Convert belt feet-per-minute and the lamp's effective cure-zone length into seconds the part spends under UV per pass.
Use it on a conveyor line when the belt speed is fixed (paced by upstream equipment) and you need to know the dwell you actually have for dose math.
It computes the seconds a point spends under the lamp given the cure-zone length and belt speed, then adds a safety margin.

Formula used

Base dwell (sec) = (cure-zone length ÷ 12) ÷ belt speed × 60
Recommended dwell = base dwell × (1 + dwell margin)

Inputs explained

Lamp cure-zone length:
Conveyor belt speed:
Dwell safety margin:

How to use the result

Use it when setting or validating belt speed for a new coating, or when back-solving the fastest line speed that still delivers the required exposure.
Dwell time alone does not guarantee cure; it must be paired with irradiance to know the actual dose, since a fast lamp and long dwell can still under-deliver energy.

Common questions

How do you calculate UV dwell time under a lamp? Convert the cure-zone length to feet, divide by belt speed in ft/min, then multiply by 60 to get seconds. A 10-inch zone at 30 ft/min gives a base dwell of 0.33 seconds before any safety margin.
What is a good UV dwell time? There is no universal number — it depends on the coating's required dose and the lamp's irradiance. The goal is enough dwell to hit the dose spec at your line speed; the calculator's margin (20% in the example) builds in headroom for lamp aging and speed drift.
Why add a dwell margin? Lamps lose output as they age, belt speeds drift, and radiometers have tolerance. A 20% margin — turning a 0.33 second base dwell into 0.40 seconds — protects against under-cure as conditions degrade between maintenance intervals.
How does belt speed affect UV cure? Dwell is inversely proportional to belt speed, so doubling the speed halves the exposure time and the delivered dose. Speed is the single biggest lever on cure, which is why it should be set from the dose requirement, not from throughput targets alone.
How do I convert required UV dose into a belt speed? Divide the required dose by the lamp's irradiance to get the needed dwell in seconds, then rearrange this formula to solve for belt speed given your cure-zone length. This calculator lets you check the resulting dwell has enough margin.

Last reviewed 2026-05-12.