Hydroponic Nutrient Calculator
Calculate nutrient solution strength for hydroponics and soilless growing.
Targets EC, PPM, and dilution ratios for all growth stages.
How hydroponic nutrients work:
Plants grown without soil get all their nutrition from water. The nutrient solution must be mixed to precise concentrations measured as EC (electrical conductivity) or PPM (parts per million). Too weak and the plants starve. Too strong and you burn the roots.
EC vs PPM conversion:
PPM (500 scale) = EC × 500
PPM (700 scale) = EC × 700
Most US meters use the 500 scale. European meters often use 700. Check your meter’s manual.
Target EC by growth stage:
| Stage | EC (mS/cm) | PPM (500) | Notes |
|---|---|---|---|
| Seedlings / clones | 0.4–0.8 | 200–400 | Very gentle — roots are fragile |
| Vegetative (early) | 0.8–1.2 | 400–600 | Increasing nitrogen demand |
| Vegetative (late) | 1.2–1.8 | 600–900 | Full veg strength |
| Flowering / fruiting | 1.8–2.4 | 900–1,200 | Shift toward P and K |
| Late flowering / ripening | 1.0–1.6 | 500–800 | Taper down before harvest |
Dilution formula:
If your concentrated stock solution is too strong, dilute it:
Volume to add = (Target EC / Stock EC) × Reservoir volume
Worked example:
Your reservoir is 20 gallons. You want EC 1.6. Your concentrate produces EC 4.0 when used straight.
Volume of concentrate = (1.6 / 4.0) × 20 = 8 gallons concentrate + 12 gallons water
pH is equally important:
- Most hydroponic crops thrive at pH 5.5–6.5
- Below 5.0 causes calcium lockout
- Above 7.0 causes iron lockout
- Adjust pH AFTER adding nutrients — nutrients change the pH
Reservoir management:
- Change the full reservoir every 7–14 days
- Top off evaporated water with plain pH-adjusted water (not more nutrient solution)
- Monitor EC daily — rising EC means the plant is drinking water faster than nutrients
- Ideal water temperature: 65–72°F (18–22°C) — above 75°F risks root rot