Fertilizer N-P-K Calculator
Calculate how much fertilizer to apply based on N-P-K ratio and target nitrogen rate for lawns and gardens.
Fertilizer N-P-K Calculator
Calculate how much fertilizer to apply based on N-P-K ratio and target nitrogen rate
Formula
Fertilizer Amount = (Target N Rate ÷ N%) × AreaBased on desired nitrogen application rate and fertilizer nitrogen content
How to Use
- 1Select fertilizer type — Choose a common fertilizer or enter custom N-P-K values.
- 2Set nitrogen rate — Use quick-set buttons or enter your target nitrogen rate.
- 3Enter area — Input the size of the area you want to fertilize.
- 4Choose units — Select your preferred area and weight units.
- 5View results — See total fertilizer needed and nutrients applied.
Frequently Asked Questions
What does N-P-K mean?
N-P-K stands for Nitrogen-Phosphorus-Potassium, the three primary nutrients in fertilizer. The numbers represent the percentage of each nutrient by weight.
How much nitrogen should I apply to my lawn?
Cool-season lawns typically need 1 lb of nitrogen per 1,000 sq ft per application. Warm-season lawns need about 0.5 lb. Never exceed 1 lb N per application.
What is the best N-P-K ratio for vegetables?
A balanced fertilizer like 10-10-10 works well for most vegetables. Leafy greens prefer higher nitrogen, while fruiting plants benefit from more phosphorus.
When should I fertilize my lawn?
Cool-season lawns: early spring and fall. Warm-season lawns: late spring through summer. Avoid fertilizing during extreme heat or drought.
Can I over-fertilize?
Yes! Over-fertilizing can burn plants, pollute waterways, and waste money. Always follow recommended rates and water in after application.