understanding ppm

just trying to understand this. nutes hav ethier own amount of nitrogen and stuff in them. the we have ppm. so how do you know what type of nutes to get and then the amount to get then the ppm to use of them? is it just a trail and error to fin dthe best combo?

Pick a good brand of nutes and follow their feeding schedule which they will give in ml per gallon but also in the ppm level that equates to. Then you know what your nute level should be for each week and how much to add to raise it.

For most plants and setups you want to start off at 1.2 strangth or less and work up until you see burning at the tips of your plants/