Lawn Fertilizer Calculator

Calculate exactly how much fertilizer your lawn needs based on area size and fertilizer type. Get the right amount for healthy, green grass.

How the Lawn Fertilizer Calculator Works

This calculator determines how much fertilizer your lawn needs based on its total area. The standard recommendation for most residential lawns is 1 pound of nitrogen per 1,000 square feet per application. We calculate the total fertilizer required based on this rate and the N-P-K ratio of common fertilizer products.

Understanding Fertilizer Numbers (N-P-K)

Fertilizer bags display three numbers separated by dashes, such as 20-5-10. These represent the percentage by weight of:

N (Nitrogen): Promotes green, leafy growth. The most important nutrient for lawns.
P (Phosphorus): Supports root development and is important for new lawns.
K (Potassium): Strengthens grass against disease, drought, and cold.

How Much Fertilizer to Apply

To apply 1 lb of nitrogen per 1,000 sq ft using a 20-5-10 fertilizer, you need 5 lbs of product per 1,000 sq ft (since 20% of 5 lbs = 1 lb nitrogen). For a 10-10-10 fertilizer, you'd need 10 lbs per 1,000 sq ft.

When to Fertilize

Cool-season grasses (Bluegrass, Fescue, Ryegrass): Fertilize in early fall (September) and late spring (May). Fall is the most important feeding.
Warm-season grasses (Bermuda, Zoysia, St. Augustine): Fertilize in late spring through summer (May-August) when actively growing.

Tips for Effective Fertilization

Always water your lawn after applying granular fertilizer to prevent burning. Use a broadcast spreader for even distribution. Avoid fertilizing before heavy rain, as nutrients will wash away. Follow the product's recommended rate and never apply more than directed.