Lawn Fertilizer Calculator
Enter your lawn's square footage, select your grass type and desired application rate, then enter the nitrogen percentage from your fertilizer bag to find out exactly how many bags you need.
How to Use This Calculator
- Measure your lawn area in square feet. Multiply length × width for rectangular areas, or use the Google Earth measurement tool for irregular shapes. Do not include garden beds, driveways, or hardscaping.
- Select your grass type. Cool-season grasses include Kentucky bluegrass, tall fescue, and perennial ryegrass. Warm-season grasses include Bermuda, zoysia, centipede, and St. Augustine.
- Choose your application rate. Most lawns do well at the moderate 1.0 lb N / 1,000 sq ft rate. Use light on sandy soils prone to leaching, or heavy for high-performance turf.
- Enter the nitrogen percentage from the first number on your fertilizer bag. A bag labeled 30-0-4 has 30% nitrogen — enter 30.
- Select your bag size and hit Calculate to see the number of bags needed, total product weight, and nitrogen applied.
How the Fertilizer Formula Works
- Nitrogen Needed (lbs):
(Lawn Area ÷ 1,000) × Application Rate - Product Needed (lbs):
Nitrogen Needed ÷ (N% ÷ 100) - Bags Needed:
CEILING(Product Needed ÷ Bag Size) - Coverage per Bag:
(Bag Size × N% ÷ 100 ÷ App Rate) × 1,000
Pro Tips
- [object Object]
- [object Object]
- [object Object]
- [object Object]
Recommended Fertilizer Products
Scotts Turf Builder All-Purpose Lawn Fertilizer — 12.5 lb
Feeds up to 5,000 sq ft; builds deep roots.
View on Amazon →Milorganite 6-4-0 Organic Nitrogen Fertilizer — 32 lb
Slow-release organic fertilizer, safe for all grasses.
View on Amazon →Scotts Snap Spreader
Broadcast spreader for even fertilizer distribution.
View on Amazon →Luster Leaf Rapitest Soil Test Kit
40-test kit for N-P-K and pH to match fertilizer to soil.
View on Amazon →Frequently Asked Questions
How much nitrogen does my lawn need per year?
Most cool-season grasses need 2–4 lbs of nitrogen per 1,000 sq ft per year, while warm-season grasses need 1–3 lbs. Split applications across 2–4 feeding dates rather than applying all at once.
What do the three numbers on a fertilizer bag mean?
The three numbers (e.g., 30-0-4) represent the percentage by weight of Nitrogen (N), Phosphorus (P), and Potassium (K). A 30-0-4 bag is 30% nitrogen. This calculator uses the nitrogen percentage to determine how much product you need to apply.
Can I over-fertilize my lawn?
Yes. Too much nitrogen causes fertilizer burn (yellow or brown streaks), excess thatch buildup, and increases disease susceptibility. Always measure your lawn area accurately and follow recommended application rates.
What is the best time of year to fertilize?
Cool-season grasses (Kentucky bluegrass, fescue, ryegrass) respond best to fall fertilization. Warm-season grasses (Bermuda, zoysia, St. Augustine) should be fertilized in late spring through summer when actively growing.