Hydroponic Nutrient PPM Calculator
Seedlings want ~400 PPM, flowering plants up to 1,400 — but your nutrient bottle says "5 mL per liter" with no mention of PPM. This converts your target PPM into actual milliliters for your reservoir size.
Calculator
Hydroponic Nutrient PPM Calculator
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Seedlings want ~400 PPM, flowering plants up to 1,400 — but your nutrient bottle says "5 mL per liter" with no mention of PPM. This converts your target PPM into actual milliliters for your reservoir size.
How to use this calculator
- Enter reservoir volume.
- Enter target PPM for the growth stage.
- Enter your nutrient's PPM per mL (from the label).
- Get mL to add.
The formula
mL = target PPM × liters ÷ (stock PPM delivered per mL of product).
What the inputs mean
The target is the concentration you want, in PPM. The volume is how much liquid you are treating. The result tells you exactly how much liquid nutrient to add.
Worked example
50 L reservoir, 800 PPM target, nutrient delivers 40 PPM per mL per liter... simplified: follow label calibration; the calculator handles the arithmetic.
Quick reference
| Stage | Typical PPM |
|---|---|
| Seedling | 300–500 |
| Vegetative | 600–1,000 |
| Flowering | 1,000–1,400 |
Crop-dependent; ramp gradually.
Where you will actually use this
Growth-stage targets in PPM are precise; "capfuls per gallon" are not.
- DWC and NFT systems
- Reservoir changes
- Growth-stage transitions
Mistakes that give wrong answers
- Changing PPM too fast between stages (ramp gradually)
- Ignoring pH while chasing PPM
Key takeaways
- Formula: Nutrient (mL) = Target PPM × Reservoir (L) ÷ Stock PPM per mL
- Remember: Crop-dependent; ramp gradually.
- Watch out for: Changing PPM too fast between stages (ramp gradually)
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
What PPM for hydroponic lettuce?
Seedlings 400–600, mature 800–1,000.
What PPM for flowering stage?
Typically 1,000–1,400 depending on crop.