Fertilizer Calculator
Calculate fertilizer requirements, application rates, and costs for your lawn or garden
Calculate Fertilizer Requirements
Lawn/Garden Area
Fertilizer NPK Ratio
Desired Application Rates
Fertilizer Bag Information
Fertilizer Application Results
Calculation: Desired N rate (43.6 lbs/acre) ÷ N% (10%) = 435.6 lbs fertilizer/acre
Total needed: 435.6 lbs/acre × 0.00 acres = 0.0 lbs
Application rate: NaN lbs per 1000 sq ft
Application Tips
Example Calculation
Lawn Fertilization Example
Lawn area: 5,000 sq ft (0.115 acres)
Fertilizer: 25-5-10 NPK
Desired N rate: 1 lb per 1000 sq ft
Bag size: 50 lbs at $25 per bag
Calculation Result
Fertilizer rate = 43.56 lbs N/acre ÷ 25% = 174 lbs/acre
Total needed = 174 × 0.115 = 20 lbs fertilizer
Bags needed = 20 ÷ 50 = 1 bag
Total cost = 1 × $25 = $25
NPK Quick Reference
Typical lawn ratios: High N for growth (20-5-10), balanced for maintenance (10-10-10)
Recommended Rates
Note: Split annual applications into 2-3 smaller doses for best results
Understanding Fertilizer Applications
NPK Nutrients Explained
Nitrogen (N)
Essential for chlorophyll production and leaf growth. Deficiency causes yellowing (chlorosis), while excess leads to rapid growth and disease susceptibility.
Phosphorus (P)
Critical for root development, flowering, and energy transfer. Deficiency results in purple leaves and poor root systems.
Potassium (K)
Regulates water uptake and disease resistance. Deficiency shows as brown leaf edges and increased susceptibility to stress.
Application Formula
Fertilizer Rate = Desired N Rate ÷ (N% ÷ 100)
This formula calculates how much fertilizer to apply based on the nitrogen content and your target nitrogen application rate.
Best Practices
Environmental Considerations
Water Protection
Excess fertilizer can leach into groundwater and surface water, causing algal blooms and aquatic dead zones.
Soil Health
Proper fertilization improves soil structure and microbial activity, leading to healthier, more resilient plants.
Balanced Application
Apply only what plants need based on soil tests to minimize environmental impact and reduce costs.