www.apogeeinstruments.com
There are some general conversion and calibration factors on this page. These are just very average numbers. So it’d just give you a general idea about how many umols your plants are getting. Not very precise but cheaper than buying a par meter.
For leds i use 0,0149. It’s the calibration factor for cree 3000K 80cri. I don’t have any of those hooked up in my fixture. I got 90cri 3000K, 80cri 4000K and 70cri 6500K. So this is a very basic estimate but i don’t think it’s that far off because this fixture grows some beautiful, dense, heavy buds. So 500-700 umols around the canopy is an acceptable estimate imo.