How grass seed calculator works
Seed bags quote coverage as a rate per area, and the rate differs hugely between jobs: a new lawn needs roughly 5 lb per 1,000 sq ft of a typical fescue-rye mix, while overseeding into existing grass uses about half that, because established plants already occupy part of the space. Enter your lawn area and the calculator applies the matching default rate.
The seed weight is area ÷ 1,000 × rate in imperial units (or area ÷ 100 × kg-per-100 m² in metric). If your bag states its own rate, override the default — species vary from about 1 lb per 1,000 sq ft for dense Kentucky bluegrass to 8 or more for some mixes, and the number printed on your bag beats any rule of thumb.
Fertilizer is computed from nitrogen, the nutrient that actually drives application rate. The standard target is 1 lb of actual nitrogen per 1,000 sq ft; a bag labeled 20% nitrogen therefore needs 5 lb of product per 1,000 sq ft. Enter the N percentage from your bag and the calculator converts the target into product weight for your lawn.