Use this engineering calculation for a transparent preliminary estimate or independent arithmetic check when geometry, materials, loads, operating conditions, and units are defined consistently.

Luminous Flux Lumens (lm)

Required number input.

Input Power Watts (W)

Required number input.

Luminous efficacy of a source in lumens per watt of electrical input power. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Efficacy Lumens Per Watt (lm/W)

The resulting efficacy lumens per watt returned as a number.

• Illuminance and lighting-power estimates depend on photometric files, geometry, reflectance, maintenance, daylight, controls, glare, spectrum, observer position, and code definitions. Lumens divided by area is not a complete lighting design.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check assumptions against drawings, measurements, current material data, and the applicable design code. Apply required load combinations and safety factors, then obtain qualified review and testing for consequential designs.

• Chiller Cop

  Chiller coefficient of performance as cooling output divided by electrical input power, in matching power units.

• Fiber Attenuation

  Optical fiber power loss in decibels from attenuation per kilometer times fiber length; excludes connectors and splices.

• Fuel Cell Efficiency

  Fuel-cell electrical efficiency from electric output energy divided by fuel lower-heating-value input energy.