Grass Seed Calculator
Find out how much grass seed to buy for a new lawn or for overseeding an existing one.
Last reviewed 2026-06-06
Sow grass seed too thin and you get a patchy lawn full of weeds; too thick and the seedlings choke each other. The right amount depends on your lawn’s area and the type of grass.
Enter your lawn size, pick a seed type and whether you’re starting fresh or overseeding. We apply the typical seeding rate for that grass and tell you how much seed to buy.
How to use the Grass Seed Calculator
- Measure the length and width of the lawn area.
- Choose your grass seed type — each has a different recommended rate.
- Select “new lawn” or “overseeding” (overseeding uses about half the seed).
- Read the weight of seed to buy, and double-check against your seed bag.
Frequently asked questions
How much grass seed do I need per square foot?
It depends on the grass. Typical new-lawn rates are about 3 lb per 1,000 sq ft for Kentucky bluegrass, 5 for a cool-season blend, and 6–8 for tall fescue. Overseeding uses roughly half. The calculator applies the right rate once you pick a type.
What is the difference between new lawn and overseeding rates?
A new lawn needs full coverage to establish from bare soil, while overseeding just thickens existing grass — so it uses about half the seed. Select the purpose above and the calculator adjusts automatically.
Can I use too much grass seed?
Yes. Over-seeding (too dense) makes seedlings compete for water, light and nutrients, leading to weak, disease-prone grass. Stick close to the recommended rate rather than “more is better”.
When should I sow grass seed?
Cool-season grasses do best sown in early autumn or spring; warm-season grasses like Bermuda prefer late spring to early summer. Always check the seed bag for your region.