Water Soluble Fertilizer Calculator
Calculate precise fertilizer mixing ratios for hydroponic and greenhouse growing
Calculate Fertilizer Requirements
N-P-K Numbers
Target Requirements
Parts per million (mg/L)
Fertilizer Recipe
Alternative Measurements
Resulting Nutrient Concentrations
⚠️ Important Notes
• Volume measurements (tablespoons) are approximate and not recommended for precision
• Use a digital scale for accurate weight measurements
• Dissolve fertilizer completely before adding to your final container
• Check and adjust pH after mixing
Calculation Formulas
Example: 200 ppm Nitrogen Solution
Given Parameters
Fertilizer: 20-8-20 (20% N, 8% P₂O₅, 20% K₂O)
Target: 200 ppm Nitrogen
Volume: 100 L water tank
Calculation Steps
1. Fertilizer concentration = 200 ppm ÷ 0.20 = 1000 mg/L = 1 g/L
2. Total fertilizer needed = 1 g/L × 100 L = 100 g
3. Resulting P₂O₅ = 1 g/L × 0.08 = 80 mg/L (35 mg/L elemental P)
4. Resulting K₂O = 1 g/L × 0.20 = 200 mg/L (166 mg/L elemental K)
Result: Add 100g fertilizer to 100L water for 200 ppm N
Common Nutrient Targets
Conversion Factors
Mixing Tips
Use a digital scale for accurate measurements
Dissolve fertilizer in small amount of water first
Use clean, sterile mixing equipment
Check and adjust pH after mixing
Store away from light to prevent algae
Keep calcium separate from phosphates/sulfates
Understanding Water Soluble Fertilizers
Benefits of Mixing Your Own
Creating custom fertilizer solutions gives you complete control over plant nutrition while saving money and improving consistency.
Key Advantages:
- • Cost savings compared to pre-made solutions
- • Precise control over macro and micronutrients
- • Consistent growing environment
- • Easier transport and storage
- • Custom formulations for specific crops
Reading Fertilizer Labels
N-P-K Numbers
The three large numbers (e.g., 20-8-20) represent nitrogen, phosphate (P₂O₅), and potash (K₂O) as percentages of total weight.
Guaranteed Analysis
Detailed breakdown on the back label showing all nutrients, including secondary and micronutrients.
Important Considerations
Water Quality
Your water source affects nutrient availability:
- • Rainwater: Clean but may lack minerals
- • Tap water: May contain beneficial minerals
- • Deionized: Provides maximum control
- • Test EC regularly for consistency
pH Management
Nutrient availability depends on pH:
- • Most nutrients available at pH 5.5-6.5
- • Check pH after adding fertilizer
- • Use pH adjusters as needed
- • Monitor throughout growing cycle
Safety & Storage
Proper handling ensures quality:
- • Store solutions away from light
- • Use sterile mixing equipment
- • Separate incompatible nutrients
- • Label solutions clearly
Calculation Methods
Basic Formula
To achieve a target concentration:
Then multiply by total volume to get weight needed
Unit Conversions
Converting between different units:
Useful for European formulations and research