measurement

Found it a while back but forgot it. I'm looking for a site that has a calculator where you can put in the ppfd of your light and what height you want and it gives you said reading. Does anyone know of this? Thanks

Just starting this thread cause of all the clutter out there. I'll be posting my questons here. You are welcome to answer with fact, opinion or both, I even welcome speculation. Just give your reasoning, if you insist on just posting your opinion or information I will simply press ignore...