Fertilizer NPK Ratio Calculator
Understand NPK ratios and calculate exactly how much fertilizer to apply to your lawn or garden.
Results
Visualization
How It Works
Every fertilizer bag has three numbers (like 10-10-10) representing the percentage of Nitrogen, Phosphorus, and Potassium by weight. The rest is filler and micronutrients. Understanding these numbers helps you feed your plants exactly what they need.
The Formula
Fertilizer (lbs) = (Area / 1,000) x Application Rate. Actual N = Fertilizer x N%.
Variables
- N (Nitrogen) — promotes leafy green growth — important for lawns and leafy vegetables
- P (Phosphorus) — supports root development and flowering — key for new plantings and blooming plants
- K (Potassium) — builds overall plant health and disease resistance — helps with stress tolerance
Tips
- Always get a soil test before fertilizing — you may already have plenty of one nutrient and too little of another.
- More fertilizer is not better. Over-fertilizing can burn plants and contaminate groundwater.
- For most home vegetable gardens, a balanced fertilizer like 10-10-10 applied at planting time is a solid starting point.
- Slow-release fertilizers feed plants gradually over weeks, which is more forgiving than liquid concentrates.
- Organic options like compost, fish emulsion, and bone meal release nutrients slowly and improve soil structure over time.