Grass Seed Calculator
Calculate how much grass seed you need for a new lawn or overseeding an existing one.
Covers all major grass types with correct seeding rates.
Why Seeding Rates Vary So Much Grass seed rates vary enormously by species, and getting this wrong wastes money or leaves a patchy, thin lawn. The difference is seed size. Kentucky Bluegrass seed is tiny, roughly 2.2 million seeds to the pound, so two pounds scatters over four million seeds across 1,000 sq ft. Tall Fescue seed is nearly ten times heavier at about 227,000 per pound, which is why it takes eight pounds to put down a comparable number.
| Grass | Seeds per pound | New lawn rate | Seeds per sq ft at that rate |
|---|---|---|---|
| Kentucky Bluegrass | ~2,200,000 | 2 lb | ~4,400 |
| Fine Fescue | ~550,000 | 4 lb | ~2,200 |
| Perennial Ryegrass | ~227,000 | 8 lb | ~1,800 |
| Tall Fescue | ~227,000 | 8 lb | ~1,800 |
| Bermuda (hulled) | ~1,800,000 | 1 lb | ~1,800 |
| Zoysia | ~1,300,000 | 2 lb | ~2,600 |
| Centipede | ~400,000 | 0.25 lb | ~100 |
Read down the last column and the logic falls out: most species land between 1,500 and 2,500 seeds per square foot, and Kentucky Bluegrass goes heavier because its seedlings are weak and many never make it. Centipede is the outlier, sown deliberately thin because it spreads by stolons and fills in on its own. Always follow the rate for your specific grass type rather than a number you remember from a different lawn.
Cool-Season vs. Warm-Season Grasses This is the most important choice for new lawn installation. Cool-season grasses (Kentucky Bluegrass, Tall Fescue, Fine Fescue, Perennial Ryegrass) thrive in the northern US (roughly north of a line from Washington DC to Kansas City to San Francisco). They grow actively in spring and fall, go semi-dormant in summer heat, and should be seeded in late summer or early fall when soil temperatures are 50–65°F. Warm-season grasses (Bermuda, Zoysia, Centipede, St. Augustine) thrive in the South and only grow when soil temperatures exceed 65–70°F. They go dormant and turn brown in winter and should be seeded in late spring.
New Lawn vs. Overseeding A new lawn on bare soil requires a full seeding rate to establish thick, competitive coverage from scratch. Overseeding, which means adding seed to an existing lawn to thicken it or repair bare spots, uses roughly half the new-lawn rate, since existing grass provides competition and you don’t need to cover every square inch from zero.
Proper Soil Preparation The most common reason for seeding failure is poor seed-to-soil contact. Till bare soil 2–3 inches deep, break up clumps, remove rocks and debris, and add starter fertilizer before seeding. After spreading seed, lightly rake it into the top ¼ inch of soil. Straw mulch helps retain moisture but should be thin enough that you can still see 50% of the soil surface.
Germination Times by Grass Type Perennial Ryegrass germinates fastest, in about 7 days under good conditions. Tall Fescue takes 10–14 days. Kentucky Bluegrass is the slowest at 14 to 21 days and requires patience. Zoysia is notoriously slow at 14–21 days or longer. Keep soil consistently moist until germination. Let it dry out once and you may lose the entire seeding.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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