Fertilizer Calculator
Calculate the perfect amount of fertilizer for your lawn. Get personalized NPK recommendations based on your grass type, lawn size, and seasonal needs.
Note: These recommendations are estimates based on general guidelines. For best results, consider a soil test to determine your lawn's specific nutrient needs. Always follow fertilizer label instructions and local regulations.
- ✓Increase grass density by 40-60% - Proper nitrogen application promotes thick, lush turf that naturally resists bare spots
- ✓Reduce weed growth by crowding out competitors - Dense, healthy grass leaves no room for weeds to establish and spread
- ✓Save $50-100/year by avoiding over-application - Precise calculations prevent wasted fertilizer and unnecessary expense
- ✓Prevent fertilizer runoff and environmental damage - Correct application rates protect waterways from nutrient pollution
- 1Measure your lawn area
Use length × width for rectangles, or try online satellite tools like Google Earth for irregular shapes. Break complex areas into smaller rectangles and add them together.
- 2Identify your grass type
Not sure? Take our grass identification quiz for personalized care recommendations. Cool-season grasses include Kentucky Bluegrass and Fescue. Warm-season grasses include Bermuda and St. Augustine.
- 3Select season and fertilization goal
Choose your current season and whether you're maintaining an established lawn, recovering from damage, or establishing new grass. The calculator adjusts NPK ratios automatically.
- 4Get your personalized fertilization plan
Click calculate to receive detailed NPK recommendations, application rates, timing advice, and safety tips tailored to your specific lawn conditions.
- 5Save or print your results
Keep your fertilization plan handy for reference at the garden center or share it with your landscaper. Results include shopping lists and seasonal schedules.
Fertilizer Calculator
Get personalized NPK recommendations for your lawn
Get Fertilizer Reminders & Tips
Receive timely reminders for fertilizer applications and seasonal lawn care advice
Seasonal Guides
Perfect timing for your region
Expert Advice
From lawn care professionals
What do NPK numbers mean on fertilizer bags?
NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K). The numbers represent the percentage of each nutrient by weight. For example, 10-10-10 means 10% nitrogen, 10% phosphorus, and 10% potassium.
How often should I fertilize my lawn?
Frequency depends on your grass type and season. Cool-season grasses typically need 3-4 applications per year (spring and fall), while warm-season grasses may need 4-5 applications during their growing season (spring through fall).
When is the best time to fertilize?
For cool-season grasses, apply in early spring and fall. For warm-season grasses, apply in late spring through early fall. Avoid fertilizing during extreme heat or drought conditions.
What's the difference between organic and synthetic fertilizers?
Organic fertilizers are derived from natural sources and release nutrients slowly over time. They improve soil health but may take longer to show results. Synthetic fertilizers provide quick results but don't improve soil structure.
Can I over-fertilize my lawn?
Yes, over-fertilization can burn your lawn, cause excessive growth, and contribute to environmental pollution. Always follow recommended application rates and avoid applying fertilizer to wet grass or before heavy rain.
How do I measure my lawn size accurately?
You can measure manually by multiplying length × width, use online mapping tools like Google Earth, or walk your lawn with a measuring wheel. For irregular shapes, break the lawn into smaller rectangles and add them together.
Should I fertilize before or after mowing?
Fertilize after mowing when the grass is shorter. This ensures better contact between the fertilizer and soil, and the shorter grass won't interfere with even distribution.
What if I don't know my grass type?
Take our comprehensive grass identification quiz to get personalized care recommendations. You can also contact your local extension office or lawn care professional for help with identification.
Do I need different fertilizers for different seasons?
Yes, seasonal fertilizers are formulated for specific needs. Spring fertilizers often have higher nitrogen for growth, fall fertilizers may have more potassium for winter hardiness, and starter fertilizers are high in phosphorus for root development.
How do I choose between different NPK ratios?
Choose based on your lawn's needs: High nitrogen (first number) for green color and growth, high phosphorus (middle number) for root development and new lawns, high potassium (last number) for stress resistance and winter hardiness.