Grass Seed Calculator
Punch in your lawn's size and the seeding rate, and get the pounds of seed to buy — whether you're starting from bare dirt or thickening up what's there.
A brand-new lawn wants about 5 lbs of seed per 1,000 sq ft. Overseeding an existing lawn takes roughly half that — try 2 to 3 lbs.
How it works
Seeding rates are quoted per 1,000 sq ft, so we take your lawn's area, divide by 1,000, and multiply by the rate. A 50-by-40 lawn is 2,000 sq ft, which at 5 lbs per 1,000 comes to 10 lbs of seed.
New lawns want a heavier rate — around 5 lbs per 1,000 sq ft — because you're covering bare ground. Overseeding an existing lawn takes about half that, roughly 2 to 3 lbs, since the grass that's already there fills in the gaps.
Seed at the home store usually comes in 5-lb bags, so we divide the pounds by five and round up. Grabbing one extra bag is cheap insurance against a thin spot you missed.
Frequently asked questions
How much grass seed do I need per square foot?
Think in thousands of square feet instead — a new lawn wants about 5 lbs of seed per 1,000 sq ft, and an overseed about half that. Enter your area and rate and the tool does the multiplying.
What's the difference between new lawn and overseed rates?
A new lawn starts from bare soil, so it needs the full rate to get solid coverage. Overseeding drops seed into grass that's already growing, so you can cut the rate roughly in half and still thicken things up.
When's the best time to seed?
Early fall is the sweet spot for cool-season grasses — warm soil, cooler air, and fewer weeds competing. Spring works too, but you'll fight more crabgrass and summer heat.
Should I buy extra seed?
A little extra rarely hurts. Beds and edges eat more than the math suggests, and having a partial bag left over means you can patch a bare spot later without a whole new trip.