Which NPK Ratio for autoflowers?

you'll need more N. assume you were doing a weighted average? that locks in ratios, but concentration can be anything depending on dilution. 15-12-26 is close to what i use but at a 650-750ppm. 650ppm will be great starting point for autoflowers. if any adjustments are needed it'll be a minor issue you can slowly adjust to -- dialing it in as needed. 15-12-26 is basically 5-4-9 ... it's a hell of a lot easier workign with ppms.. lol N 125-130 is about as high as you will need P 50 ish K 180-190ish Ca 100+ Mg 80+ S 110+ Some of that will vary due to tap water... i have had water.. if you use RO or have much better water than me, you may need a bit more of Ca or Mg for example. 600-650 is good range to start.. react to plant to further dial in your formula... some environmental factors can impact this too... rate of transpiration if extremely low or high may call for some slight adjustments. the goal is to feed the right amount per 24 hours (or any uniform increment of time on average).. so if rate of uptake is slow, probably need to increase concentration slightly and vice versa if extremely high.