Calculator
Example data table
| Tank | N–P₂O₅–K₂O (%) | Basis | Target ppm | Stock g/L | Loss % |
|---|---|---|---|---|---|
| 50 L | 20–20–20 | N | 150 | 200 | 2 |
| 100 gal | 10–30–20 | P₂O₅ | 60 | 250 | 1 |
| 200 L | 18–6–18 | K₂O | 180 | 180 | 0 |
Formula used
How to use this calculator
- Read the N–P₂O₅–K₂O numbers from your fertilizer label.
- Enter your tank volume and select liters or gallons.
- Pick a basis nutrient and type its target ppm.
- Enter your concentrate strength, in grams per liter.
- Optionally add handling loss and fertilizer price per kilogram.
- Press Calculate to see grams, dosing volume, and downloads.
Why Concentrate Accuracy Matters
Concentrated feeding reduces storage space and speeds mixing, but errors scale fast. A small measuring mistake can shift ppm targets, stressing roots and changing growth rate. This calculator links label percentages to tank volume, so dosing stays repeatable across seasons, crop stages, and reservoir sizes. It also helps teams follow the same recipe across shifts.
Reading N–P₂O₅–K₂O Numbers Correctly
Fertilizer labels often report phosphorus and potassium as oxides, not elemental forms. Using the printed values keeps results consistent with common labeling practice. If a recipe lists elemental P or K, convert before entry, then verify with an EC meter and plant response. Keep notes on water alkalinity, because bicarbonates can change nutrient availability.
Choosing An Effective Target Ppm
Targets depend on crop type, light, temperature, and starting water quality. Begin with a moderate ppm for the chosen basis nutrient, then adjust gradually after observing leaf color and new growth. The tool also reports resulting N, P₂O₅, and K₂O ppm from your product, helping you spot imbalances early and avoid overcorrecting. Recheck after topping up the tank.
Building A Stable Stock Solution
Stock strength is entered as grams of fertilizer per liter of concentrate. Stronger stocks reduce dosing volume but can exceed solubility, especially in cold water or hard water. Mix with warm water, add fertilizer slowly, and stir until clear. Label containers with date, strength, and product name. The batch option shows grams to dissolve for a planned stock volume, supporting consistent refills.
Controlling Cost And Consistency
Cost per tank matters when feeding frequently. Enter price per kilogram to estimate each mix, then compare products at the same target ppm to judge value. Use the handling loss field to cover residue in scoops, funnels, or hoses, and to reduce underfeeding. Saving CSV or PDF results supports recordkeeping, repeat orders, and troubleshooting when plants react to a formula change.
Pair the calculated mL per liter rate with a marked syringe or graduated jug. Calibrate your scale occasionally. When changing brands, run one tank at the old recipe, then transition slowly to prevent sudden EC swings and pH surprises too.
FAQs
Should I target ppm or EC?
Use ppm for nutrient planning and EC for quick verification. Start with a ppm target for the basis nutrient, then measure EC after mixing. Record both values so you can repeat the same solution with different water sources.
What does the basis nutrient mean?
The basis nutrient is the one you want to match your target ppm. The calculator sets fertilizer grams to hit that nutrient, then reports the resulting levels of the other two nutrients based on the same dose.
How strong can my concentrate be?
It depends on fertilizer solubility, temperature, and water hardness. If crystals form, lower the grams per liter or mix warmer. Keep containers sealed and shake before dosing to maintain uniform strength.
Can I mix two fertilizers together?
Yes, but calculate each product separately, then combine their gram amounts in the tank. Recheck the combined ppm and EC after mixing. Avoid pairing products that precipitate, such as calcium with high sulfates or phosphates.
Why add handling loss?
Handling loss accounts for fertilizer stuck in scoops, funnels, or the stock container. Adding a small percentage improves repeatability. If you use precise scales and rinsing, set it to zero.
How do I store my results?
Click the CSV or PDF buttons after calculating. Save files with crop name and date. Keeping a log helps diagnose deficiencies, compare batches, and train staff on consistent mixing.