UV Curing calculator

UV LED Array Power Density Calculator

UV LED arrays are sold in many lengths and configurations, but the comparable spec across vendors is W/in of UV optical output (the W/in that actually reaches the part, derated for thermal margin). This calculator does that conversion in one step so a process engineer can compare a 12 W/in array from one vendor against a quoted 8 W/in array from another, or scale a known-good 16 W/in design to a wider product.

What this calculator does

  • Calculate UV LED array optical power density (W per inch of array length) — the spec that lets you compare LED arrays head to head independent of array length.
  • Use it during LED array sourcing or retrofit sizing to compare quotes from different vendors, or to scale a known-good design to a new product width.
  • Returns nameplate UV W/in for an LED array and the effective W/in at the part after a thermal / aging derate.

Formula used

  • Nameplate density = UV optical power ÷ array length (W/in)
  • Effective density at part = nameplate × thermal/aging derate

Inputs explained

  • Array UV optical power: Vendor's quoted UV optical output across the band — not wall-plug kW.
  • Array effective length: Useful UV-emitting length along the belt direction; usually slightly less than housing length.
  • Thermal / aging derate: Headroom for sustained operation; 85–95% of new optical at design current.

How to use the result

  • Use during LED retrofit sourcing to normalize across vendor quotes, when scaling a known design to a new product width, and to estimate dose from a vendor spec sheet before a sample arrives.
  • Optical W/in is a useful comparison number, not a dose number. Dose at the part also depends on focal distance, reflector / lens design, and dwell — convert to mW/cm² with the array vendor's intensity-vs-distance curve, then use UV Dose to get the actual dose math.

Common questions

  • How does W/in translate to mW/cm² at the part? Divide W/in by the array's effective beam width at the working distance, with unit conversion (W to mW = ×1,000; in to cm = ÷2.54). Vendors usually publish an intensity-vs-distance curve — use that rather than back-of-envelope. Typical 16 W/in array at 5 mm from part = 8–12 W/cm² (8,000–12,000 mW/cm²).
  • What W/in do I need? Driven by your dose target and dwell time. Quick sizing: line speed × dose target = required intensity-time product. 4–8 W/in is light-duty (UV inkjet, low-dose adhesives); 12–20 W/in is mainstream production (web press, conveyor coating); 25–40 W/in is for thick coatings or fast lines.
  • Why a thermal derate? Vendor 'rated' optical output is often at peak instant current with the array thoroughly heat-sunk. Real production runs continuous and the array runs warmer; output drops 5–15% from rated. Build the derate into design sizing so you don't ship an array that hits dose at startup but droops by lunch.
  • Does W/in vs mW/cm² matter for chemistry compatibility? Yes — some chemistries are intensity-sensitive (cure threshold not met at low irradiance even with same total dose). Most modern UV LED chemistries are formulated for the high intensity that LED arrays deliver; older chemistries developed for mercury may underperform on LED. Validate with the chemistry vendor before locking the array spec.

Last reviewed 2026-05-12.