How much grass seed do you need?

The formula

Seed needed = lawn area ÷ 1,000 × adjusted rate per 1,000 sq ft. The adjusted rate is the base rate divided by pure live seed: purity % × germination %. A bag that is 98% pure and 90% germinating contains about 88% pure live seed, so you need a little more of it.

Starting rates

The calculator uses common establishment rates, not cultivar-specific recommendations. Tall fescue, Kentucky bluegrass, perennial ryegrass, fine fescue, bermudagrass, zoysiagrass, centipedegrass, and buffalograss are included. St. Augustine is usually established by sod or plugs rather than seed, so it is not listed.

Seed labels, local extension guidance, and the cultivar in the bag can change the right rate. If the label gives a rate for your situation, use the label.

Bags are rounded up

The bag count rounds up to the next whole bag. That can leave leftover seed; keep it dry and cool, and check the germination date before using it next season.