Per the manufacturer:  For moderate-climate grasses like bluegrass, rye, and fescue, apply four pounds of FoxFarm Happy Frog Premium Lawn Organic Fertilizer 8-2-6 (one small box) to every 150 square feet in March, May, July, and October. For tropical grasses like Bermuda and St. Augustine, apply the same amounts in April, May, June, July, and August. Spread evenly with a garden spreader and water thoroughly. This would mean that you would need about 372 lbs per application to treat a 14,000 sq ft lawn, or 21 of the 18 lb bags. So a 4-lb covers 150 square feet and the 18 lb covers 675 sq ft.