| Example | Volume (L) | Inputs | N (ppm) | P (ppm) | K (ppm) | Added solids (ppm) | EC est. (mS/cm) |
|---|---|---|---|---|---|---|---|
| Balanced feed | 10 | 20 g of 20‑20‑20 | 400.0 | 174.6 | 332.0 | 2000.0 | 4.000 (500 scale) |
| Leafy focus | 15 | 12 g of 24‑8‑16 | 192.0 | 27.9 | 106.3 | 800.0 | 1.600 (500 scale) |
| Two-part style | 20 | 18 g of 15.5‑0‑0 + 10 g of 0‑0‑50 | 139.5 | 0.0 | 207.5 | 1400.0 | 2.000 (700 scale) |
- Dose conversion: In stock mode, grams added = (Stock g/L × Stock mL) ÷ 1000.
- Elemental ppm: ppm = (grams × fraction × 1000) ÷ volume(L).
- Label conversion: P = P2O5 × 0.4364 and K = K2O × 0.8301.
- Added solids: product ppm ≈ (total grams × 1000) ÷ volume(L) × soluble fraction.
- EC estimate: EC(mS/cm) ≈ Added solids ppm ÷ PPM scale (500 or 700).
- Enter the final tank volume in liters.
- Choose direct dosing or stock dilution mode.
- For each fertilizer you used, switch Include on.
- Type the label percentages as N, P2O5, and K2O.
- Enter grams (direct) or stock concentration and mL (stock).
- Press Calculate to show results above the form.
- Use CSV or PDF buttons to save the computed report.
Why nutrient strength matters in everyday growing
Nutrient strength links what you weigh to what roots actually receive. A label may look balanced, yet the final ppm can be too weak for fast growth or too strong for tender seedlings. Consistent strength supports stable uptake, predictable leaf color, and smoother crop transitions across stages.
Reading labels and converting to usable numbers
Most products list N–P2O5–K2O. This calculator converts the oxide values to elemental P and K so mixes can be compared on the same basis. When you combine products, each one contributes a share of N, P, and K based on its percentage and the grams added to the final tank.
Using EC estimates with a realistic mindset
The EC figure here is an estimate from added soluble solids and a chosen meter scale (500 or 700). It is useful for trend tracking and recipe repetition. Real EC depends on water minerals, temperature, and the chemistry of salts. Check with an actual meter when precision is critical.
Mix strategy for seedlings, leafy greens, and fruiting plants
Seedlings typically prefer lower ppm and gentler ratios. Leafy crops often tolerate higher N, while fruiting stages commonly benefit from more K relative to N. Use the ratio output as a quick signal, then adjust grams rather than chasing a single perfect number in every situation.
Example data you can replicate in your tank
The table below shows sample inputs and typical outcomes. Use it to validate your workflow, then swap in your own products and volumes. Small gram changes can move ppm quickly in small reservoirs.
| Scenario | Volume (L) | Recipe | N (ppm) | P (ppm) | K (ppm) |
|---|---|---|---|---|---|
| Starter | 5 | 5 g of 20-20-20 | 200.0 | 87.3 | 166.0 |
| Leafy | 10 | 10 g of 24-8-16 | 240.0 | 34.9 | 132.8 |
| Fruiting | 20 | 18 g of 15.5-0-0 + 10 g of 0-0-50 | 139.5 | 0.0 | 207.5 |
1) What does ppm mean in this calculator?
ppm is mg/L. The calculator converts your grams of nutrient into mg, then divides by the final solution volume in liters to estimate nutrient concentration.
2) Why are P and K lower than the label numbers?
Labels list P2O5 and K2O. This tool converts them to elemental P and K using standard factors, so the values are comparable to elemental nutrient targets.
3) How accurate is the EC number?
It is a practical estimate based on added soluble solids and the selected meter scale. Water hardness, temperature, and salt types can shift real EC readings.
4) Should I use direct mode or stock mode?
Use direct mode when weighing grams into the tank. Use stock mode when dosing from concentrate; the tool converts stock g/L and mL into grams added.
5) Can I combine multiple fertilizers safely?
Yes, but avoid known incompatibilities in concentrated form. Keep separate stocks when needed and mix into final water. Always add products one at a time with agitation.
6) What soluble fraction should I choose?
Use 100% for fully soluble salts. Reduce it if a product contains fillers or slow-release granules. This setting mainly influences added-solids and EC estimates.
7) How do I hit a target ppm?
Start with a simple recipe, calculate, then scale grams proportionally. Doubling the grams roughly doubles ppm, as long as volume stays the same.