About this tool
Grass Seed Calculator is a free, in-browser tool that tells you how much grass seed a lawn needs. Enter the lawn area directly or as length × width, choose a grass type, pick new lawn or overseeding, and set your bag size — it returns pounds of seed, number of bags and the effective seeding rate. Nothing is uploaded; everything is computed locally.
Each grass type carries a typical seeding rate in pounds per 1,000 square feet: Kentucky bluegrass 2, tall fescue 6, perennial ryegrass 7, Bermuda 1.5 and fine fescue 4. Pounds of seed = (area ÷ 1000) × rate × factor, where the factor is 1 for a new lawn and 0.5 for overseeding, since overseeding an existing lawn needs about half the seed. Bags = ceil(pounds ÷ bag size), rounded up because seed is sold in whole bags.
Use the new-lawn rate when starting from bare soil and the overseeding rate to thicken a thin, established lawn. Seeding rates vary a little by cultivar and blend, so treat the result as a close estimate and check the rate printed on your seed bag.