that depends on Pot size, plant size, and growth of the plant. If your using a solo cup , id say about 2 week ( basicly how long it would take your root system to fill the pot and leach out all the nutes) if your in a 1-2 gal id say mabye 20-30 days ( again going off root growth), 3-5 gal Could possibly have enough to make it through a full grow without having to add anything your plant isnt telling you it wants IMHO.