I have a 405W led light, I use a vegetative growth...

Seek out the maker of your light. If that option is unavailable to you, i see that many manufacturers of LEDs recommend a distance of around 24inches from seedlings ...so around 60 cm. However i have often seen people vary between 20-24 inches. So if 60 cm feels too high, bring it down slightly. If your plants begin to stretch at all youll know the light needs lowering...better than burning them from too close. Happy vegging!🌱✌️

I was gonna say same as @stick , I use the hand test method n it's never failed me bud . Good luck with the grow 👍👍👍

Hi @OneLeaf! Each LED manufacturer has its own recomendations about this. One of the best way to find the right distance is to do the universal "hand test". If by placing your hand on top of your plant's summits, you get hot / your hand burns, then this distance needs to be increased. Later, your plant will spread and you might need to increase this distance for better coverage. If you don't notice heat (hand-test) nor light-stress (weird colors on leaves) then you're good to go with your current plant<--->light distance. Hope this will help, keep us up-to-date and happy growing 👊