How this calculator works
Seed is spread at a rate measured in pounds per 1,000 square feet, and the right rate depends on the grass species (small seeds like bluegrass need far less weight than big seeds like tall fescue). We divide your area by 1,000 and multiply by the rate. Overseeding existing turf uses about half the rate of a new lawn.
Worked example: a 50 × 20 ft lawn is 1,000 ft². A new tall fescue lawn at 8 lb per 1,000 ft² needs 8 lb of seed, which is two 5 lb bags.
Tips before you buy
- Seed-to-soil contact is everything: rake the soil, spread the seed, lightly rake it in, and roll it so it is pressed into the surface.
- The best times to seed are late summer to early fall for cool-season grasses, and late spring to early summer for warm-season grasses such as bermudagrass.
- Keep the seedbed consistently damp until the grass is up, which may mean light watering two or three times a day.
- A starter fertilizer helps seedlings establish. Avoid weed-and-feed products on new seed unless the label says it is safe.
Tools & materials for this project
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Frequently asked questions
How much grass seed do I need per square foot?
It depends on the grass. Tall fescue is about 0.008 lb per ft² (8 lb per 1,000 ft²), and Kentucky bluegrass about 0.0025 lb per ft². The calculator uses typical new-lawn rates.
How much seed do I need for overseeding?
Roughly half the new-lawn rate, since you are filling in gaps in existing turf.
Can I put down too much grass seed?
Yes. Too much seed makes seedlings compete and thin out, and increases disease. Stick to the label rate.
Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.