This grass seed calculator works out the pounds of seed to buy and the bag count for a new lawn or overseeding, by grass type. No sign-up. The working is shown under every number.
Quick example: a 50 × 20 ft lawn (1,000 sq ft) seeded with tall fescue at the new-lawn rate needs 7 lb of seed — one 20 lb bag ($48.00) covers it at the example prices.
| Item | Buy | Cost |
|---|---|---|
| Estimated total | $0.00 |
Rates are the typical label rates for each grass — your seed bag's label wins if it says different, so edit the rate to match it.
Estimate only — not a guarantee. Mistakes are possible, so always check the quantities with your supplier or a builder before you buy or build.
It depends on the grass, because the seeds are very different sizes. Typical label rates for a new lawn: tall fescue about 7 lb per 1,000 sq ft, perennial ryegrass about 8 lb, a general lawn mix about 5 lb, Kentucky bluegrass only about 2.5 lb (its seeds are tiny), and bermuda about 1.5 lb. Overseeding an existing lawn takes roughly half the new-lawn rate. Pick your grass and job type in the calculator — it sets the rate for you, and you can adjust it to match your seed bag's label.
At the tall fescue new-lawn rate of 7 lb per 1,000 sq ft, 5,000 sq ft needs 35 lb of seed — two 20 lb bags at this calculator's example prices ($96.00). The same lawn overseeded at half rate needs 17.5 lb, so one 20 lb bag is enough.
By the weight on the label, not the bag's physical size — bags of the same size hold very different weights of different grasses. Work out the pounds you need first (this calculator does that), then buy bags that add up to at least that weight. A little leftover seed keeps in a cool dry place for patching bare spots later in the season.
For cool-season grasses (fescue, bluegrass, ryegrass) early fall is best — warm soil, cool air and fewer weeds — with early spring as the second choice. Warm-season grasses like bermuda go down in late spring once the soil is warm. Seed needs consistent moisture for the first two to three weeks, so time it when you can water lightly every day.
| Lawn job | Seed needed | 20 lb bags | Total |
|---|---|---|---|
| 1,000 sq ft, tall fescue, new lawn | 7.0 lb | 1 | $48.00 |
| 1,000 sq ft, Kentucky bluegrass, new lawn | 2.5 lb | 1 | $48.00 |
| 1,000 sq ft, tall fescue, overseeding | 3.5 lb | 1 | $48.00 |
| 5,000 sq ft, tall fescue, new lawn | 35.0 lb | 2 | $96.00 |
Rates: tall fescue 7 lb per 1,000 sq ft new lawn / 3.5 overseeding; Kentucky bluegrass 2.5 / 1.5; perennial ryegrass 8 / 4; bermuda 1.5 / 1; lawn mix 5 / 2.5. Always check the rate printed on your seed bag — blends vary.
These figures are planning estimates only — not a guarantee and not professional advice. Mistakes are possible, including through an error in this calculator. Always check the quantities, sizes, spacings and depths with your supplier, a licensed builder, and your local building code before you buy materials or start work. The owner of this site accepts no responsibility or liability for any loss, cost, damage, injury, wasted material or failed inspection that results from using these estimates. Prices are examples to start from, not live prices or quotes.