Its difficult to give you an exact figure without using a par meter.
I'd need to set a board at 60 watts and measure it but due to lockdown I can't get access to my meter lol.
Seedlings/clones 100 - 200 umol per m2/s
Vegetative 200 - 400 umol per m2/s
Flowering 600 - 800 umol per m2/s
I calculated the distance required by using different par maps that are online.
An unfortunate truth.
Luckily, with normal white led’s, a lux meter is all you really need to know that you’re in the ballpark. Mine cost me around $35.
It’s an additional calculation from lux to ppfd and I’m sure, not quite as accurate, but it’s good enough to for me to estimate that my plants are getting a little over 30 DLI right now.
HLG has an article on their site with lux to ppfd calculators:
https://horticulturelightinggroup.com/blogs/calculators/converting-lux-to-ppfd
The ppfd to DLI:
https://horticulturelightinggroup.com/blogs/calculators/converting-ppfd-to-dli
As far as how high I have mine?
I have them all the way at the ceiling and the plants on the floor.
Running them closer might be better for some, but I decided to prioritize ppfd consistency along the vertical axis of my growing space.
Though it may not answer this particular question on lighting, I found that the videos by Dr. Bruce Bugbee (Director of the Crop Physiology Laboratory at Utah State University) on Apogee’s (they make PAR meters and other quantum sensors) youtube channel to be insanely informative. Please do check them out.