Lawn
Grass Seed Calculator
Pick your grass type and the calculator uses its actual seeding rate. Overseeding an existing lawn takes roughly half the seed of a new one.
Overseeding uses roughly half the seed of a new lawn.
Pounds per bag, from the label.
Quantity estimate for planning and buying. Rates vary by variety, region and product — check the label on what you actually buy.
Seeding rates are not one number
The single biggest reason people over- or under-buy seed is treating "grass seed" as one product. Seeding rate depends on the species, and the spread is large: tall fescue goes down at 9 lb per 1,000 ft² for a new lawn, Kentucky bluegrass at 2 lb, and centipede at half a pound. That is an eighteen-fold difference.
Seed size drives it. Bluegrass has roughly 2.2 million seeds per pound; tall fescue has about 230,000. You need far less bluegrass by weight to put the same number of seeds on the ground.
| Grass | New lawn | Overseeding | Season |
|---|---|---|---|
| Kentucky bluegrass | 2 lb | 1 lb | Cool |
| Perennial ryegrass | 8 lb | 5 lb | Cool |
| Tall fescue | 9 lb | 5 lb | Cool |
| Fine fescue | 5 lb | 3 lb | Cool |
| Bermudagrass (hulled) | 2 lb | 1 lb | Warm |
| Zoysia | 2 lb | 1 lb | Warm |
| Centipede | 0.5 lb | 0.25 lb | Warm |
| Bahiagrass | 8 lb | 5 lb | Warm |
New lawn or overseeding?
A new lawn on bare soil gets the full rate, because every seed has to establish a plant. Overseeding an existing lawn uses about half — you are filling gaps, not building turf, and a heavy overseed just creates seedlings competing with each other and with the grass already there.
Going heavier than the recommended rate does not give you a thicker lawn. It gives you crowded, spindly seedlings that shade each other out and are more prone to damping-off disease. This is one of the few places in gardening where more is actively worse.
Timing matters more than quantity
You can buy exactly the right amount of the right seed and still fail by putting it down at the wrong time of year.
- Cool-season grasses (fescue, bluegrass, ryegrass): late summer to early autumn is the best window by a wide margin — warm soil, cooling air, less weed competition. Early spring is a distant second.
- Warm-season grasses (bermuda, zoysia, centipede, bahia): late spring to early summer, once soil temperature is consistently above 65°F. Autumn seeding of warm-season grass fails.
Seed needs consistent moisture in the top half-inch until germination — light watering once or twice a day, not a soaking every few days. That is 5-7 days for ryegrass and up to 21 for bluegrass, which is worth knowing before you start.
Common questions
How much grass seed do I need for 1,000 square feet?
It depends entirely on the grass. Tall fescue needs about 9 lb for a new lawn, perennial ryegrass 8 lb, fine fescue 5 lb, Kentucky bluegrass 2 lb, and bermudagrass 2 lb. Halve those figures for overseeding.
How much seed for a 5,000 square foot lawn?
For tall fescue, 45 lb for a new lawn or 25 lb to overseed. For Kentucky bluegrass, 10 lb new or 5 lb to overseed.
Can I use too much grass seed?
Yes. Over-seeding produces crowded seedlings that compete with each other for light, water and nutrients, and it raises the risk of damping-off disease. A heavy rate gives you a worse lawn than the correct rate, not a thicker one.
When is the best time to plant grass seed?
Late summer to early autumn for cool-season grasses like fescue and bluegrass. Late spring to early summer for warm-season grasses like bermuda and zoysia, once soil is reliably above 65F.