How much grass seed do you need?
Pick your grass, add your lawn areas, get pounds of seed and bags instantly.
How do I calculate how much grass seed I need?
Multiply the lawn area in square feet by the seeding rate for your grass and divide by 1,000. The rate is given in pounds per 1,000 square feet: a 5,000 square foot lawn of tall fescue at 7 pounds per 1,000 square feet needs 5,000 × 7 ÷ 1,000 = 35 pounds of seed — two 20 lb bags, or five 7 lb bags.
How much grass seed per 1,000 square feet?
For a new lawn: tall fescue and perennial ryegrass about 6 to 9 pounds, fine fescue 4 to 5, Kentucky bluegrass 1 to 3, Bermudagrass and zoysiagrass 1 to 2, bahiagrass 5 to 10 and centipedegrass just 0.25 to 0.5. The calculator uses the middle of these university extension ranges; the label on your seed bag gives the rate for that mix — pick From the bag and type it in.
How much seed do I need to overseed a lawn?
About half the new-lawn rate, since the existing grass already covers most of the ground: 3 to 4 pounds of tall fescue per 1,000 square feet instead of 7. Choose Overseeding and the rates for the listed grasses are halved. For a lawn that is more bare soil than grass, use the new-lawn rate.
When is the best time to plant grass seed?
Cool-season grasses such as tall fescue, Kentucky bluegrass and ryegrass do best from late summer to early fall, when the soil is warm and the air is cooler; spring is second best. Warm-season grasses such as Bermuda, zoysia, centipede and bahia go in from late spring to early summer, once the soil is warm.
Is more seed better?
No. Seeding far above the rate crowds the seedlings, which then compete for water and light and are more prone to disease. Spread the seed evenly — half the seed in one direction and half across it — and keep the soil moist until the grass is up.
Worked example: a 4,200 square foot lawn
For a new tall fescue lawn at 7 pounds per 1,000 square feet, 4,200 square feet needs 4,200 × 7 ÷ 1,000 = 29.4 pounds, which is 2 bags of 20 lb or 5 bags of 7 lb. Overseeding the same lawn at half the rate takes 14.7 pounds. A Bermudagrass lawn of that size at 1.5 pounds per 1,000 square feet needs only 6.3 pounds, or 3 bags of 3 lb. Note that the calculator rounds up to whole bags but the seed you actually spread is the pound figure.
How do pounds per 1,000 square feet convert to other units?
Seeding rates also appear per acre or per square meter. An acre is 43,560 square feet, so 7 pounds per 1,000 square feet is 305 pounds per acre. One pound per 1,000 square feet is 4.88 grams per square meter (453.592 grams in a pound, 92.903 square meters in 1,000 square feet), so the same 7 pounds is about 34 grams per square meter, which is the unit the metric mode uses.
Why do the rates for one grass differ between sources?
University extension services publish ranges, not single values: tall fescue is listed at about 6 to 9 pounds per 1,000 square feet depending on the source, and the calculator uses a value inside that range. The right number depends on the seed mix, the seed size, the soil preparation and how quickly you want a dense lawn. A mixed bag also contains several species, so the label rate for the mix is the better guide, entered under From the bag.
Common mistakes when buying grass seed
Measuring the whole property instead of the lawn, which counts the house, drive and beds. Applying the new-lawn rate to a lawn that only needs overseeding, which wastes seed and crowds seedlings. Using the rate of one grass for another: the rates differ by a factor of ten or more between centipedegrass and tall fescue. Dividing by 1,000 twice, or not at all, which moves the answer by a factor of a thousand. Buying by the bag coverage on the label without checking which rate it assumes.
Sources and related calculators
Sources: NC State Extension, “Carolina Lawns”, UMass Extension, “Seeding Rate Considerations”, and Penn State Extension for the seeding rates; overseeding at 25 to 50 percent less is from NC State. Rates are guides: your seed label and local extension office decide. Related: fertilizer calculator, sod calculator, topsoil calculator and lawn watering calculator.