Enter your lawn size and grass type. Get pounds of seed, bags to buy, and what to charge for the job.
To work out how much grass seed you need, divide your lawn area by 1,000, then multiply by the seeding rate for your grass type. A 5,000 square foot lawn being overseeded with tall fescue is 5 × 3.75, or 18.8 pounds of pure seed. Buy about 24 pounds: a bag is typically 85% pure live seed, and you lose some to spreader overlap and the bare patches you find on site.
Seeding rates are given in pounds per 1,000 square feet, the unit used on North American seed labels. Cool season grasses run from 2 to 9 pounds; warm season grasses are far lower, often under 2.
| Grass | New lawn, lb per 1,000 sq ft | Overseed, lb per 1,000 sq ft |
|---|---|---|
| Tall fescue | 5 to 9 | 3 to 4.5 |
| Perennial ryegrass | 6 to 9 | 3 to 4.5 |
| Tall fescue + Kentucky bluegrass mix | 4 to 6 | 2 to 3 |
| Fine fescue | 4 to 5 | 2 to 2.5 |
| Kentucky bluegrass | 2 to 3 | 1 to 1.5 |
| Bahiagrass | 5 to 10 | – |
| Bermuda (hulled) and zoysia | 1 to 2 | 1 to 2 |
| Centipede | 0.25 to 0.5 | – |
Sources: Penn State Extension, NC State Extension, University of Minnesota Extension, Clemson Cooperative Extension. Where sources differ, the calculator uses the midpoint of the range.
Extension services do not recommend perennial ryegrass on its own. It germinates fast, which is why it sells, but a pure ryegrass lawn thins out. Use it in a mix.
Seed is measured per 1,000 square feet, not per square foot. Tall fescue at 7 pounds per 1,000 works out at 0.007 pounds per square foot, about a tenth of an ounce. That is why nobody sells it that way: measure the lawn, divide by 1,000, and multiply by the rate.
An acre is 43,560 square feet, which is 43.56 thousands. Multiply the rate by 43.56. Tall fescue works out at about 305 pounds for a new lawn and 163 pounds for an overseed.
| Grass | New lawn, per acre | Overseed, per acre |
|---|---|---|
| Tall fescue | 305 lb | 163 lb |
| Perennial ryegrass | 327 lb | 163 lb |
| Tall fescue + KBG mix | 218 lb | 109 lb |
| Fine fescue | 196 lb | 98 lb |
| Kentucky bluegrass | 109 lb | 54 lb |
| Bahiagrass | 327 lb | – |
| Bermuda (hulled) and zoysia | 65 lb | 65 lb |
| Centipede | 16 lb | – |
Overseeding takes roughly half the seed of a new lawn, because you are thickening turf that already exists rather than covering bare soil. For tall fescue that is about 3.75 pounds per 1,000 square feet instead of 7.
The half rule is a rule of thumb, not a standard. Three cases where it breaks:
More seed is not better. Seedlings that come up too thick compete with each other, stay weak and thin out anyway.
Put down the rate for your grass and your job: 3 to 4.5 pounds per 1,000 square feet to overseed tall fescue, 5 to 9 to seed it from bare ground. Add about 10% for spreader overlap and the bare patches you find on site, and split the seed into two passes at right angles rather than emptying the bag in one.
Switch the calculator to Price the job and it adds labour and margin: (hours × your crew rate + seed cost) × (1 + overhead and profit), never below your minimum. Hours come from the seeding method, and those rates are planning figures, not measured data – replace them with your own once you have tracked a few jobs.
A 5,000 square foot overseed with a slit seeder is 38 minutes of work: $34 of labour at $55 an hour, two $60 bags of seed, plus 35% overhead and profit, prices at $208. Three things belong on the estimate as separate lines:
Sanity check: the median lawn fertilization line item on Tofu is $117, typically $60 to $240, across 10,121 line items from 84 lawn businesses. Fertilization is the closest comparable in our data – there are no overseeding line items. A small overseed near $200 sits in the right band; $600 does not.
Seed labels carry a figure called pure live seed. It is the share of the bag that is actual seed capable of germinating, after subtracting inert matter, weed seed and dead seed. Good seed runs 90% or higher; discount mixes can drop to 70%, which means a 20 pound bag delivers 14 pounds of working seed. The calculator assumes 85% and you can change it under "Your numbers".
A 50 pound bag of tall fescue covers about 5,500 square feet on bare ground, or 10,300 square feet when overseeding. The same bag of Kentucky bluegrass covers 15,450 square feet, because its rate is far lower. The coverage printed on the bag is roughly 30% higher than this, because it assumes clean seed and perfect spreading.
| Bag | Tall fescue, new | Tall fescue, overseed | Kentucky bluegrass, new |
|---|---|---|---|
| 5 lb | 550 sq ft | 1,050 sq ft | 1,550 sq ft |
| 10 lb | 1,100 sq ft | 2,050 sq ft | 3,100 sq ft |
| 20 lb | 2,200 sq ft | 4,100 sq ft | 6,200 sq ft |
| 50 lb | 5,500 sq ft | 10,300 sq ft | 15,450 sq ft |
These figures assume 85% pure live seed and 10% for spreader overlap, wind and the bare patches you find once you are out there – the calculator's defaults. It is also why two bags at the same weight and different prices are not the same product: compare the pure live seed percentage, not the sticker.
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