How do you calculate UV dose uniformity?

Take your maximum dose reading minus your minimum reading to get the spread, then divide by the average dose and multiply by 100. With a 1450 max, 950 min, and 1200 average, the spread is 500 mJ/cm² and non-uniformity is 41.7%.

What is a good UV dose uniformity number?

For most adhesive and coating processes you want non-uniformity under 10-15%. The 41.7% in the worked example is poor and signals a reflector, focal-height, or lamp-aging problem that needs correcting before you set a process spec.

Why does UV uniformity matter more than average dose?

Cure is driven by the lowest dose any point receives, not the average. A 1200 mJ/cm² average looks healthy, but the 950 cold spot may sit below the coating's cure threshold and fail adhesion or leave a tacky edge.

What causes poor UV dose uniformity across a web?

Common causes are a degraded or misaligned reflector, uneven lamp aging along its length, incorrect focal height, part geometry that shadows edges, and dirty quartz plates or lamp envelopes.

How many points should I measure for a uniformity map?

Measure at least across the full working width plus the leading and trailing edges of the part. More points catch localized cold spots; a coarse two-point check can easily miss the true hot and cold extremes.

UV dose uniformity vs UV irradiance uniformity — what's the difference?

Dose uniformity (mJ/cm²) accounts for both intensity and time under the lamp, so it reflects total energy delivered. Irradiance uniformity (mW/cm²) is instantaneous intensity only; two points with equal irradiance can still get different doses if belt speed or shadowing varies.

UV Curing calculator

UV Dose Uniformity Calculator

UV dose uniformity tells you how evenly UV energy lands across a part or web as it passes under the lamp. It is calculated by taking the spread between the highest and lowest radiometer readings and dividing by the average dose. Process engineers and coating line operators track it because an under-cured cold spot will tack, blush, or fail adhesion tests even when the average dose looks fine on paper. A single-point radiometer reading hides this problem entirely, which is why cross-web and cross-part mapping matters.

What this calculator does

Quantify UV dose uniformity across a work surface from radiometer pass min, max, and average - see whether the worst spot still cures.
Use it after a profiling pass to prove the cold corner of a fixture or belt still receives enough dose, or to justify reflector / lamp-spacing changes.
It computes the percentage variation in delivered UV dose between the coldest and hottest measured points across a cure surface.

Formula used

Spread = max dose − min dose (mJ/cm²)
Non-uniformity (%) = spread ÷ average × 100

Inputs explained

Minimum dose reading (cold spot):
Maximum dose reading (hot spot):
Average dose across the cure surface:

How to use the result

Use it after a multi-point radiometer mapping pass on a new part fixture, a wider web, or after a lamp or reflector change to confirm even cure edge to edge.
It only reflects the specific points you measured; if your grid misses a shadowed edge or a reflector dead zone, real uniformity is worse than the number suggests.

Common questions

How do you calculate UV dose uniformity? Take your maximum dose reading minus your minimum reading to get the spread, then divide by the average dose and multiply by 100. With a 1450 max, 950 min, and 1200 average, the spread is 500 mJ/cm² and non-uniformity is 41.7%.
What is a good UV dose uniformity number? For most adhesive and coating processes you want non-uniformity under 10-15%. The 41.7% in the worked example is poor and signals a reflector, focal-height, or lamp-aging problem that needs correcting before you set a process spec.
Why does UV uniformity matter more than average dose? Cure is driven by the lowest dose any point receives, not the average. A 1200 mJ/cm² average looks healthy, but the 950 cold spot may sit below the coating's cure threshold and fail adhesion or leave a tacky edge.
What causes poor UV dose uniformity across a web? Common causes are a degraded or misaligned reflector, uneven lamp aging along its length, incorrect focal height, part geometry that shadows edges, and dirty quartz plates or lamp envelopes.
How many points should I measure for a uniformity map? Measure at least across the full working width plus the leading and trailing edges of the part. More points catch localized cold spots; a coarse two-point check can easily miss the true hot and cold extremes.

Last reviewed 2026-05-12.