Grass seed calculator
Add your lawn areas and pick the grass and the job. You get the pounds of seed, the bags to buy and the rate per acre, using the seeding rates published by Penn State, Maryland, Florida and Clemson extension.
Inputs
Result
Grass seeding rates
Pounds of seed per 1,000 sq ft, from university extension guides, and what each would take for your lawn at the middle of the range.
| Grass | New lawn | Overseeding | Per acre, new | Your lawn |
|---|
Sources: Penn State Extension, Lawn Establishment, Table 1; University of Maryland Extension, Lawn Renovation and Overseeding; UF/IFAS, Establishing Your Florida Lawn (LH013), Table 2; Clemson HGIC, Zoysiagrass. Overseeding rates in italics are half the new-lawn rate, where no overseeding rate is published.
How it is worked out
A 50 x 20 ft lawn is 1,000 sq ft. Tall fescue on bare soil goes down at 6 to 8 lb per 1,000 sq ft, so 7 lb at the middle of the range: two 5 lb bags. Overseeding the same lawn takes 4 lb. Per acre, the new-lawn rate is about 305 lb.
New lawn or overseeding
A new lawn on bare soil needs the full rate. Overseeding thickens a lawn that is already there, so it takes less: the University of Maryland gives 4 lb of tall fescue, 1.5 lb of Kentucky bluegrass and 2.5 lb of fine fescue per 1,000 sq ft, about half the new-lawn rates. Penn State gives 4 to 6 lb of perennial ryegrass for overseeding or renovation.
More seed is not better. Seeding well above the rate crowds the seedlings, which then compete with each other and are more prone to disease. Small seed like bluegrass and centipede has many more seeds to the pound, which is why its rate is so much lower than tall fescue's.
When to seed
- Cool-season grasses: late summer to early fall is best. Missouri Extension gives August 25 to October 10, with Labor Day the ideal; spring seedings struggle with weeds and summer heat.
- Warm-season grasses: late spring to early summer, once the soil is warm. Bermudagrass and centipede seed are slow to come up in cool soil.
Rates assume good quality seed. Check the label: the percent germination and purity tell you how much of the bag will grow. For a quicker lawn, the sod calculator works out sod instead, and the topsoil calculator the soil to put under it.
Questions
How much grass seed do I need per 1,000 square feet?
It depends on the grass. For a new lawn: tall fescue 6 to 8 lb, Kentucky bluegrass 2 to 3 lb, perennial ryegrass 4 to 5 lb, fine fescue 4 to 5 lb (Penn State); Bermudagrass 1 to 4 lb, Bahiagrass 5 to 10 lb, centipede 0.25 to 1 lb (UF/IFAS).
How much grass seed do I need for overseeding?
About half the new-lawn rate. The University of Maryland gives 4 lb of tall fescue, 1.5 lb of Kentucky bluegrass and 2.5 lb of fine fescue per 1,000 sq ft.
How many pounds of grass seed per acre?
Multiply the rate per 1,000 sq ft by 43.56. Tall fescue at 7 lb per 1,000 sq ft is about 305 lb per acre; Kentucky bluegrass at 2.5 lb, about 110 lb.
How many pounds of grass seed per square foot?
Very little: tall fescue at 7 lb per 1,000 sq ft is 0.007 lb, about a tenth of an ounce, per square foot. Rates are given per 1,000 sq ft for that reason.
How much area does a 5 lb bag of grass seed cover?
At tall fescue's new-lawn rate of 7 lb per 1,000 sq ft, about 700 sq ft; overseeding at 4 lb, 1,250 sq ft. Kentucky bluegrass at 2.5 lb covers 2,000 sq ft.
Can I put down too much grass seed?
Yes. Seedlings packed too thickly compete for water and light and are more prone to disease. Stay within the recommended range.
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