Grass Seed Calculator
Enter your lawn area and a seeding rate, and this calculator estimates how many pounds of grass seed you need and how many bags to buy. New lawns are seeded at roughly double the overseed rate, so it also shows both scenarios side by side. Always check the rate printed on your seed bag — different grass species and blends vary — and treat this as a planning estimate.
Seeding job
Defaults: 5 lb/1,000 for a new lawn, 2.5lb/1,000 for overseeding a generic cool-season blend. Use your seed bag's label rate for the best accuracy.
Grass seed needed
25 lb
5,000 sq ft × 5 lb/1,000 sq ft
Bags to buy
2
at 20 lb / bag
Coverage
5k
thousand sq ft
Seed detail
New lawn vs overseed (lb, default rates)
Compare scenarios
Run the same calculation with two or three input sets side by side. Differences are highlighted; every number comes from the same tested formula as the calculator above.
| Input | Scenario A | Scenario B |
|---|---|---|
| Area Sq Ft | ||
| Rate Per1000 | ||
| Mode | ||
| Bag Lbs |
How it works
Seed needed is calculated as your lawn area divided by 1,000, multiplied by the seeding rate in pounds per 1,000 square feet. Seeding rates are almost always given per 1,000 sq ft on the bag and in extension charts, so a 5,000 sq ft lawn at 5 lb/1,000 needs 5 × 5 = 25 pounds. Measure your actual grassed area — subtract driveways, beds, and the house footprint — because overestimating area wastes seed and underestimating leaves thin patches.
The rate depends on what you are doing and which grass you are planting. This tool defaults to a generic cool-season blend at 5 lb per 1,000 sq ft for a new (bare-soil) lawn and 2.5 lb per 1,000 sq ft for overseeding an established lawn. Toggle between the two modes to switch the default, or type in the exact rate from your seed label, which is the most accurate number to use since it reflects that product's seed count and species mix.
Bags to buy is your total pounds divided by the bag weight, rounded up to the next whole bag, since seed is sold in fixed sizes. It is common to buy a little extra for reseeding thin spots a few weeks after germination. The calculator keeps the underlying math unrounded and only rounds the displayed pounds, so the totals stay consistent whether you seed the whole lawn at once or in sections.
Frequently asked questions
What is the difference between the new-lawn and overseed rates?+
A new lawn is seeded on bare soil where there is no existing grass, so it needs enough seed to establish full coverage from scratch — commonly around 5 lb per 1,000 sq ft for a cool-season blend. Overseeding spreads seed into an existing lawn to thicken it or repair thin areas, so it uses roughly half the rate, about 2.5 lb per 1,000 sq ft, because the standing turf already provides part of the coverage. These are typical starting points; your seed bag's label rate takes priority over any general figure.
Do all grass types use the same seeding rate?+
No. Seeding rates vary widely by species because seed size and seeds-per-pound differ. Tall fescue is often seeded around 6–8 lb per 1,000 sq ft, Kentucky bluegrass closer to 2–3 lb, perennial ryegrass around 5–9 lb, and fine fescues in between. Warm-season grasses like Bermuda are seeded at much lower weights. Because of this variation, we let you enter your own rate rather than guessing from the species, and the defaults here reflect a generic cool-season mix, not any single grass.
When is the best time to seed?+
For cool-season grasses, late summer to early fall is usually the best window: warm soil speeds germination while cooling air and fewer weeds help seedlings establish before winter, with early spring as a second choice. Warm-season grasses are best seeded in late spring to early summer once soil is reliably warm. This calculator only estimates quantity, not timing — check your regional university extension service for the recommended seeding dates and grass types for your area.