Formula used
The blend solver minimises combined N, P₂O₅, and K₂O differences. Product availability adjusts nutrient release before comparing supplied amounts. Soil-test guidance should remain the final decision source.
How to use this calculator
- Select field planning or liquid mixing mode.
- Enter the treatment area and recommendation units.
- Add soil credits and realistic nutrient-loss assumptions.
- Choose fertilizer presets or enter custom grades.
- Review shortages, excesses, costs, and application timing.
- Confirm rates with soil tests and local guidance.
Example data
| Example | Area | Target N-P₂O₅-K₂O | Products | Applications |
|---|---|---|---|---|
| Vegetable garden | 500 m² | 120-60-90 kg/ha | 18-46-0 DAP and 46-0-0 urea | 3 |
| Lawn maintenance | 5,000 ft² | 4-1-2 lb/1,000 ft² equivalent | 20-5-10 blend | 4 |
| Fertigation tank | 200 L | 150-50-150 ppm | 20-20-20 soluble fertilizer | 1 tank |
NPK fertilizer calculator FAQs
What does NPK mean?
NPK identifies nitrogen, phosphate, and potash percentages in fertilizer. A 10-10-10 product contains ten percent of each nutrient. The remaining weight includes carriers and other materials.
Why are phosphorus and potassium shown as P₂O₅ and K₂O?
Most fertilizer labels report phosphorus and potassium using oxide equivalents. Soil reports may use elemental values instead. Always match the recommendation and label conventions.
Can this calculator mix several fertilizers?
Yes. Add multiple product rows with editable grades and prices. The balanced option estimates a non-negative blend.
How are organic fertilizers handled?
Set the product type to organic and reduce availability. This models first-year nutrient release. Actual release still depends on environmental conditions.
What is nutrient-use efficiency?
Efficiency estimates how much applied nutrient reaches the crop. Lower efficiency increases the calculated requirement. Use realistic values from local guidance.
Should nutrient loss be added separately?
Yes, when leaching, volatilisation, runoff, or fixation is expected. Avoid double-counting losses already included in recommendations. Conservative assumptions reduce overapplication risk.
Why can one nutrient exceed its target?
Fixed NPK ratios rarely match every target perfectly. Meeting one nutrient can oversupply another. Multiple products usually improve nutrient balance.
How does the bag calculation work?
Exact bags show the mathematical quantity required. Purchase bags round upward to whole packages. Cost uses the rounded purchase quantity.
Can I calculate a liquid fertilizer mix?
Yes. Enter tank volume, density, fertilizer grade, and desired ppm. The result shows product mass and volume.
Does this replace a soil test?
No. The calculator converts recommendations into practical product quantities. Soil tests and local agronomic advice remain essential.
What safety checks should I make?
Confirm maximum rates, irrigation timing, salt sensitivity, and compatibility. Keep fertilizer away from waterways and drains. Follow every product label before application.