The Lighting Research Center at Rensselaer Polytechnic Institute (LRC) invites you to make use of this free online calculator.

The calculator allows luminaires to be compared based on equal photosynthetic photon flux density (PPFD). PPFD for plants is analogous to photopic illuminance on a work surface in an architectural application. The calculator includes the analysis of luminaire-specific and application-specific metrics, which provide the best available information regarding any given horticultural luminaire’s performance. To make these calculations, it uses an IES file and spectral power distribution (SPD).

The calculator results include a comparison with other commercially-available luminaires (example below), the number of luminaires needed to meet the target PPFD, the mounting height that will result in the most efficacious application, the cost of ownership, and the payback period.


High-power high-pressure sodium (HPS) luminaires are the most commonly used light sources in greenhouses and indoor grow facilities, but an increasing number of light-emitting diode (LED) horticultural luminaires have entered the market. The Lighting Research Center at Rensselaer Polytechnic Institute (LRC) created a framework for evaluating and comparing horticulture luminaires. The LRC developed a computer program to evaluate horticulture luminaires using this framework. This calculator lets you evaluate any horticulture luminaire using the same methods.

Sponsored by

The LRC provides this calculator to assist in the comparison of luminaires, but does not recommend any particular product.

The calculator results are not warrentied to result in the predicted performance.

The calculator results are dependent on certain assumptions, which are described in the methodology section of the LED and HID Horticultural Luminaire Testing Report.

Some luminaires are pre-programmed into the calculator for convenience. For those that were tested by the LRC, the information is based on testing one sample product. See procurement and testing information in the LED and HID Horticultural Luminaire Testing Report. Other information, as noted, is provided by luminaire manufacturers.

It is left to the grower to make sure the mounting height is high enough to prevent thermal damage to the crop.