Fertilizer Calculator
Fertilizer NPK (from bag label)
Common Fertilizer Products & Application Rates
Pounds of product per 1,000 sq ft to achieve 1 lb N
| Product (NPK) | Lbs per 1,000 sqft | N Applied | P Applied | K Applied |
|---|---|---|---|---|
| 10-10-10 | 10.0 lbs | 1.0 lb | 1.0 lb | 1.0 lb |
| 16-4-8 | 6.25 lbs | 1.0 lb | 0.25 lb | 0.5 lb |
| 24-0-6 | 4.17 lbs | 1.0 lb | 0 lb | 0.25 lb |
| 29-0-4 | 3.45 lbs | 1.0 lb | 0 lb | 0.14 lb |
| 46-0-0 (Urea) | 2.17 lbs | 1.0 lb | 0 lb | 0 lb |
| 15-15-15 | 6.67 lbs | 1.0 lb | 1.0 lb | 1.0 lb |
| 6-2-0 (Milorganite) | 16.67 lbs | 1.0 lb | 0.33 lb | 0 lb |
How We Calculate This
This fertilizer calculator uses established formulas and industry-standard data to provide accurate estimates.
- Enter your specific values into the calculator fields above
- Our algorithm applies the relevant formulas using your inputs
- Results are calculated instantly in your browser — nothing is sent to a server
- Review the detailed breakdown to understand how each factor affects your result
These calculations are estimates based on standard formulas. For critical decisions, always consult a qualified professional.
How to Convert Oven Recipes to Air Fryer
The calculator uses the NPK percentage on the fertilizer bag to determine how much product delivers your desired nitrogen rate per 1,000 square feet.
The basic rule:
- Product per 1,000 sq ft = desired lbs of N ÷ (N% / 100)
- Total product = (product per 1,000) × (total area / 1,000)
- Bags needed = total product ÷ bag weight, rounded up
- Example: 1 lb N from a 24-0-6 requires 1 ÷ 0.24 = 4.17 lbs of product per 1,000 sq ft
- P and K applied are calculated proportionally from the same application rate
Most lawns need 2-4 lbs of nitrogen per 1,000 sq ft per year, split across 3-4 applications. Never apply more than 1 lb of nitrogen per 1,000 sq ft in a single application to avoid burning.
When Would You Use This Calculator?
This fertilizer calculator is designed for anyone who needs quick, reliable estimates without complex spreadsheets or professional consultations.
- When you need a quick estimate before committing to a purchase or project
- When comparing different options or scenarios side by side
- When planning a budget and need to understand potential costs
- When you want to verify a quote or estimate you've received from a professional
- When teaching or learning about the concepts behind these calculations
Frequently Asked Questions
What do the NPK numbers mean?
NPK stands for Nitrogen-Phosphorus-Potassium. A 24-0-6 fertilizer is 24% nitrogen, 0% phosphorus, and 6% potassium by weight. The remaining percentage is filler and carrier material.
How much nitrogen should I apply to my lawn?
Cool-season grasses (fescue, bluegrass) need 2-4 lbs N per 1,000 sq ft per year. Warm-season grasses (bermuda, zoysia) need 3-5 lbs per year. Apply 0.5-1 lb N per 1,000 sq ft per application.
Can I apply too much fertilizer?
Yes. Over-fertilizing causes fertilizer burn (brown/dead patches), excess runoff into waterways, and weak shallow root growth. Follow the calculated rate and water in after application.
When should I fertilize my lawn?
Cool-season lawns: September (most important), November, and spring. Warm-season lawns: late spring through summer when actively growing. Avoid fertilizing dormant grass.