Grass seed calculator
Pounds of seed for a new lawn or an overseed, by grass type.
Calculator
Detailed breakdown
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How to use this calculator
Measure
Measure the lawn in feet, pick your grass type and say whether you are seeding bare soil or overseeding.
Calculate
Once you hit calculate, results update as you type. Change any number to compare options instantly.
Order
Print the estimate and take it to your supplier. Quantities are rounded up so you don't come up short.
Seeding rates, and why more seed gives you less lawn
Seed is sold by weight but applied by rate per 1,000 square feet, and that rate varies enormously by species — because the seeds themselves vary so much in size. Tall fescue and perennial ryegrass go down at about 9 pounds per 1,000 square feet. Kentucky bluegrass, whose seed is tiny, needs only 3. Hulled bermuda needs about 1.5.
A 50 by 40 foot lawn is 2,000 square feet, so a new tall fescue lawn takes 18 pounds of seed. Overseeding an existing lawn uses half the rate — 9 pounds — because you are thickening a stand that already exists, not building one from nothing.
The instinct to add extra seed for insurance backfires. Sow too thickly and the seedlings compete with each other for water, light and root space, and you get a crowded, weak stand that thins out within a season and is more prone to damping-off disease. The label rate is a maximum, not a suggestion.
Seed has to touch soil to germinate. Broadcasting onto an unprepared surface leaves most of it sitting on thatch or hard ground where it dries out or feeds birds, which is why a lightly raked, loosened bed beats a heavier sowing rate every time. Germination is slower than most people expect: perennial ryegrass shows in about 5 to 10 days, tall fescue in 7 to 12, and Kentucky bluegrass can take three to four weeks. Do not conclude at day ten that the seed failed and sow it again on top.
Timing outranks quantity by a wide margin. Cool-season grasses — fescue, bluegrass, ryegrass — go down in early fall, when soil is still warm, nights are cooling and weed pressure has dropped. Warm-season grasses like bermuda want late spring, once soil temperatures are reliably above 65°F. Seed at the wrong end of the year and the correct rate won't save it. Then keep the surface consistently moist until germination: light, frequent watering, not deep soaks.
Frequently asked questions
How much grass seed for 2,000 square feet?
About 18 pounds of tall fescue for a new lawn, or 9 pounds to overseed. Kentucky bluegrass needs only about 6 pounds for the same area, because its seed is much smaller.
How much seed do I need to overseed?
Half the new-lawn rate. You are thickening existing turf rather than establishing it from bare soil.
Is more grass seed better?
No. Overseeded stands compete with themselves for water and light, thin out within a season and are more prone to disease. Treat the label rate as a maximum.
When is the best time to plant grass seed?
Early fall for cool-season grasses like fescue and bluegrass. Late spring for warm-season grasses like bermuda, once soil is reliably above 65°F.
How often should I water new grass seed?
Lightly and frequently — enough to keep the surface consistently moist until germination, which is more effective than occasional deep soaks.
Sources
Formulas and material assumptions on this page follow published industry guidance: