GRASS SEED
How much grass seed do I need?
Pounds of seed = (area in square feet ÷ 1,000) × the seeding rate for your species. The rate is the one number this page will not supply for you, because it belongs to the grass you are sowing and the job you are doing — a new lawn, an overseed and a repair patch all take different rates, and the species differ from each other more than most people expect.
Your rate comes from one of two places, both of which are better than a generic table: the seed label or bag, which usually prints a seeding rate for new lawns and a lower one for overseeding, or your state extension service, which publishes rates for the species that actually grow in your region.
The calculation, at whatever rate you have
| If your label says | New lawn | Overseeding |
|---|---|---|
| 2 lb per 1,000 sq ft | 8 lb | 4 lb at half rate |
| 3 lb per 1,000 sq ft | 12 lb | 6 lb at half rate |
| 5 lb per 1,000 sq ft | 20 lb | 10 lb at half rate |
| 8 lb per 1,000 sq ft | 32 lb | 16 lb at half rate |
Read the table as arithmetic, not as a recommendation: each row is 4,000 ÷ 1,000 × rate. The "half rate" column is simply the common pattern where an overseed uses less seed than a new lawn — check whether your label states that, rather than halving on your own.
Worked example
A 4,000 sq ft lawn being overseeded, with a label that gives 5 lb per 1,000 sq ft for a new lawn and 2.5 lb per 1,000 sq ft for overseeding: 4,000 ÷ 1,000 = 4, and 4 × 2.5 = 10 lb of seed.
That is the entire calculation. Everything else — working out the area, subtracting beds and paths — is the same measuring you do for any material on this site.
Measuring the area, including the awkward bits
Measure the lawn in simple shapes and add them: rectangles as length × width, circles as π × radius², triangles as base × height ÷ 2. Subtract beds, paths, the driveway and the ground under shrubs. On an overseed, the existing grass does not come off the area — you are seeding over all of it — but bare patches that you are repairing separately should be measured on their own and seeded at the repair rate.
Things that change the outcome more than the math
- Seed-to-soil contact. Seed sitting on top of thatch germinates poorly no matter how much you bought. Rake or core-aerate first.
- Coverage of the seed. A thin topdressing or a light rake-in is the usual advice; birds and runoff take the rest.
- Watering. Frequent light watering until germination, then deeper and less often. This is the step that decides whether the seed you calculated actually becomes lawn.
- Time of year. Cool-season and warm-season grasses have different windows, and sowing outside the window wastes seed regardless of the rate.
- Buying more than one cultivar. If you are blending varieties, keep each variety's own rate and total them.
Related calculators
Sod calculator if you are laying turf instead of sowing · How many square feet in a pallet of sod for the turf equivalent of this question · Coverage calculator for the area-and-subtraction arithmetic.
Seeding rates are deliberately not quoted: they vary by species and by job, and the label or your extension service is the source that fits your seed. The arithmetic is from 1,000 square feet as the rate basis.