Grass Seed Calculator — How Much Grass Seed Do I Need?
Wondering how much grass seed do I need for your lawn? Enter your lawn's size, pick whether you're starting a new lawn or overseeding a thin one, and this free grass seed calculator tells you exactly how many pounds of seed to buy — plus how many bags of common sizes you'll need. Results update instantly as you type.
Enter your numbers
Your results
| Bag size | Bags to buy |
|---|---|
| 5 lb bag | — |
| 10 lb bag | — |
| 20 lb bag | — |
| 50 lb bag | — |
Estimated amount: seed rates vary by grass species, blend, and soil conditions — always check the rate on your seed bag's label and treat this as a planning estimate.
How to use this calculator
Type your lawn area in square feet. If you don't know it, enter the lawn's length and width in the optional fields and the area fills in automatically (length × width). Subtract any beds, patios, or walkways that won't be seeded — results update instantly as you type.
Next, pick your seeding type: a new lawn on bare soil uses 6 lb per 1,000 sq ft, while overseeding a thin existing lawn needs about half that, 4 lb per 1,000 sq ft. If your seed bag recommends a different rate, choose Custom rate and enter it.
Buy the bags rounded up — the bag table shows how many of each common bag size cover your lawn. A little leftover seed is fine; it keeps for years stored cool and dry.
How it works
The math is simple: seed (lb) = net area (sq ft) ÷ 1,000 × rate (lb per 1,000 sq ft), where net area = lawn area − area to subtract (floored at zero). So 2,000 sq ft at 6 lb per 1,000 sq ft needs 2 × 6 = 12 lb of seed.
Bag counts round up to the next whole bag: bags = ceil(seed lb ÷ bag size), since you can't buy part of a bag. The presets reflect typical published ranges for common cool-season blends (new lawn 5–10 lb/1,000 sq ft; overseeding 3–5 lb/1,000 sq ft). These are estimates: the exact rate depends on your grass species, seed blend, soil preparation, and watering, so follow your seed bag's label for the final answer.
Frequently asked questions
How much grass seed do I need per 1,000 sq ft?
For a new lawn on bare soil, most seed blends need about 5-10 pounds per 1,000 sq ft; this calculator defaults to 6 lb per 1,000 sq ft, which sits in the middle of that range for common tall fescue and bluegrass blends. For overseeding a thin existing lawn, you typically need only half that rate, around 3-5 lb per 1,000 sq ft. Always check your seed bag's label, since exact rates vary by grass species and brand.
Is the seeding rate different for a new lawn vs overseeding?
Yes. A new lawn on bare soil needs a full rate (roughly 6-10 lb per 1,000 sq ft depending on the seed blend) because there is no existing grass to fill in. Overseeding thickens an existing thin lawn, so a half rate of about 3-5 lb per 1,000 sq ft is enough. Using the full new-lawn rate when overseeding wastes seed and can cause overcrowded, weak seedlings.
Can you put down too much grass seed?
Yes. Spreading seed too thick causes seedlings to compete for water, light, and nutrients, which produces weak, disease-prone grass. Stick to the rate on the seed bag's label (or this calculator's defaults) rather than adding extra seed just in case. If you have patchy areas, reseed those specific spots instead of doubling the whole lawn.
How do I measure an odd-shaped lawn for grass seed?
Divide the lawn into simple rectangles (and right triangles, where area = 1/2 x base x height), calculate each piece, and add them up. For curved lawns, multiply the average of the longest and shortest lengths by the average width. Subtract beds, patios, driveways, and walkways. It is better to slightly overestimate: leftover seed keeps for years in a cool, dry place.
When is the best time to plant grass seed?
As general guidance: cool-season grasses (tall fescue, bluegrass, ryegrass) do best seeded in early fall, when warm soil meets cooler air; spring is a workable second choice. Warm-season grasses (bermuda, zoysia, centipede) should be seeded in late spring to early summer, once nights stay warm. These are broad guidelines, not guarantees - check with your local garden center for your specific climate and variety.