Fertilizer label → elemental ppm

What a dose actually delivers in ppm of each element, from the guaranteed analysis on the label.

Units

Label & dose

Guaranteed analysis, % by weight. P and K are labelled as oxides (P₂O₅, K₂O) in most countries.

Product form
g/L

Delivered ppm (mg/L)

Compare with stage
N50 ppmbelow target

Dashed box: cited target 160–200 mg/L

P43.6 ppmabove target

Dashed box: cited target 30 mg/L

K124.5 ppmwithin target

Dashed box: cited target 60–175 mg/L

Ca0 ppm
Mg0 ppmbelow target

Dashed box: cited target 35–70 mg/L

S0 ppm
This is what one product adds. Real feeds combine products and your source water; the cited ranges are for the whole solution. The flower P range is contested between research groups.
How this is calculated

ppm = g/L × %element × 10; P = P₂O₅ × 0.4364; K = K₂O × 0.8301

  • Oxide factors are molar-mass ratios: 2·P / P₂O₅ = 0.4364 and 2·K / K₂O = 0.8301.
  • ppm here means mg of element per litre of finished solution.

Cited targets

From the genetics.guru grow library, in the units each source used. Grades: strong and moderate are peer-reviewed; community practice is untested.

Ask Grow Guru about thisQuestions about fertilizer label → elemental ppm? Answers come from the same cited library.