Calculator inputs
Example data table
| Scenario | Volume | Targets (ppm) | Fertilizers | Recipe result (g) |
|---|---|---|---|---|
| Balanced vegetative feed | 10 L | N 150, P2O5 50, K2O 200 | Calcium Nitrate + MKP + Potassium Nitrate | 6.63 + 0.96 + 3.64 |
| Two-ingredient quick mix | 5 L | Solve N 120, P2O5 40 (K byproduct) | MAP + Potassium Nitrate (Solve NP) | Calculated by tool output |
| Simple single product | 20 L | N 100 (P2O5, K2O optional) | Urea only | Calculated by tool output |
Example rows are for illustration. Always verify product labels and local recommendations.
Formula used
- Nutrient needed (g) = Target ppm × Volume (L) ÷ 1000
- Nutrient supplied (g) = Fertilizer mass (g) × (Analysis % ÷ 100)
- With three fertilizers, the calculator solves a 3×3 system to match N, P2O5, and K2O.
- With two fertilizers, it matches a chosen nutrient pair, and reports the third as a byproduct.
Nutrient targets and why ppm matters
ppm is milligrams per liter, so it scales cleanly with volume. When you set N, P2O5, and K2O in ppm, you are defining nutrient concentration rather than guessing spoonfuls. This calculator converts ppm to grams of nutrient needed, then calculates fertilizer masses that supply those grams from label analyses.
Interpreting fertilizer analyses correctly
Most labels report nitrogen as N, phosphorus as P2O5, and potassium as K2O. A 13-0-46 product contains 13% N and 46% K2O by weight. The tool treats each ingredient as a source vector and solves for the masses that satisfy your targets. Use three complementary sources when possible to avoid oversupplying a third nutrient.
Three-ingredient solving for predictable outcomes
With three ingredients, the calculator solves a 3×3 system to match all three targets simultaneously. If the matrix becomes unsolvable or produces negative masses, the selected products do not span the target space. Swap one ingredient for a more focused source (for example, a pure phosphate or a pure potash product) to regain a valid solution.
Two-ingredient blends and byproduct nutrients
Two ingredients can precisely match only two nutrients at a time. Choose the pair that matters most for your crop stage and water quality. The calculator reports the third nutrient as a byproduct so you can compare against your desired profile and decide whether to adjust with a third ingredient or lower targets.
Example data you can test immediately
Example input: 10 L, targets N 150 ppm, P2O5 50 ppm, K2O 200 ppm. Suggested set: Calcium Nitrate, MKP, Potassium Nitrate. Typical result: 6.63 g, 0.96 g, and 3.64 g. Achieved ppm should align closely with targets after rounding.
FAQs
1) What does ppm mean in this recipe?
ppm equals mg/L. The calculator converts ppm targets to total grams of nutrient needed using your mix volume, then computes fertilizer masses that supply those grams from label percentages.
2) Why does the tool use P2O5 and K2O instead of P and K?
Most fertilizer labels report phosphorus as P2O5 and potassium as K2O. Using label forms avoids conversion errors and keeps the math consistent with the numbers printed on your product.
3) My result shows a warning about negative amounts. What should I do?
A negative amount means the chosen fertilizers cannot meet your targets simultaneously. Try swapping one ingredient for a different analysis, add a third ingredient, or use two-ingredient mode and accept a byproduct nutrient.
4) Can I use a fertilizer not listed?
Yes. Select a Custom Fertilizer option and enter the N-P2O5-K2O percentages from your label. The calculator will treat it like any other ingredient during solving.
5) Are grams and ounces both supported?
Yes. Choose grams or ounces for display. The table also shows grams for precision and includes per-liter dosing so you can scale to different tank sizes easily.
6) Why doesn’t the recipe include calcium, magnesium, or micronutrients?
This tool focuses on N, P2O5, and K2O from common analyses. You can add separate supplements for Ca, Mg, and micros, then re-check overall EC and compatibility for your system.
7) How accurate is the “Achieved ppm” output?
It is accurate for the N-P2O5-K2O math based on your inputs. Real-world results vary with product purity, moisture, and measuring error, so weigh carefully and verify with your crop response.