EstimatorKitFree grass seed calculator
Grass seed in pounds by species, not by guesswork
Choose the grass and the job and this returns the pounds of seed, the whole bags that come to, and what one bag covers at that rate. Species is the first input because seeding rates run from 0.4 lb to 8 lb per 1,000 square feet and the difference is seed size, not need — a pound of Kentucky bluegrass holds 2.2 million seeds and a pound of tall fescue 227,000. Overseeding halves the rate, and the starter fertilizer is counted alongside.
- 100% free
- No signup
- 9 grass species
- New and overseed rates
- Starter fertilizer counted
Full rate: nothing else is holding the ground and every square inch has to be covered from seed.
The first number on the bag. An 18-24-12 starter is 18. the nitrogen rate published turf establishment guidance puts down at seeding, and it moves with the soil test — ground already high in phosphorus wants a plain nitrogen source rather than a starter analysis.
Seed to buy
1 × 25 lb bag
- Seed the rate calls for
- 24 lb
- Left in the last bag
- 1 lb
- Applied rate
- 6 lb / 1,000 ft²
- One bag covers
- 4,167 ft²
24 lb is what the rate asks for and 25 lb is what 1 whole bag contains. The gap is not waste: seed keeps two to three years in a cool dry place with the bag closed, and the leftover is what the thin spots get in six weeks when you can see which ones there are.
What that puts on the ground
- Seeds per square inch
- 16.7
- Seeds per square foot
- 2,400
- Seeds in a pound
- 400,000
- Up in
- 7–14 days
Seed count is why the rates on this page range from 0.4 to 7 lb for the same 1,000 square feet. Weight is the unit the bag is sold in; seeds per square inch is what the ground actually receives, and it is the number two different species can be compared on.
Starter fertilizer
- Product needed
- 22.2 lb
- Bags
- 1 × 50 lb
- Spreader setting works out at
- 5.56 lb / 1,000 ft²
At 18% nitrogen it takes 5.56 lb of product to lay down the 1 lb of actual nitrogen — halve the analysis and you double the bag weight for the same feed, which is the whole reason the rate is written in pounds of nitrogen rather than pounds of bag.
Rates here are volume-neutral: seed is bought by weight and spread by area, so nothing on this page depends on how much soil is underneath. What the ground needs before any of it goes down — leveling, an amendment, a compost pass — is measured on the compost calculator.
How to work out a seeding rate
Say which of the three jobs this is
Sowing bare soil, overseeding a lawn that is thin, and patching dead spots are three different sums. New ground takes the full rate. Overseeding takes half of it, because the grass already there is doing most of the covering. Patching takes the full rate but only over the bare ground: four dead patches of 3 by 4 ft are 48 square feet, not the 5,000 square foot lawn they are sitting in, and treating them as the lawn is how people end up buying twenty times the seed they need.
Pick the grass, then override the rate from the bag if it differs
Choosing the species fills in its published rate — 2.5 lb per 1,000 square feet for Kentucky bluegrass, 7 for tall fescue, 0.4 for centipede. Those differ by weight rather than by need: bluegrass seed runs 2.2 million seeds to the pound and tall fescue only 227,000, so a tenth of the weight is a comparable number of plants. The rate stays editable because a bag of a specific cultivar blend carries its own tag, and the tag wins.
Measure the ground and read pounds, bags and what one bag covers
Length and width, a diameter, or a square footage you already know. The result is the pounds the rate asks for, the whole bags that come to at the size you buy, and how much is left in the last one — the leftover is deliberately visible, because it is what the thin spots get six weeks later once you can see which spots they are. Leave the starter fertilizer box ticked and the same area produces the pounds of product needed to lay down 1 lb of nitrogen per 1,000 square feet.
Technical specifications
| Species covered | Nine: cool-season blend, Kentucky bluegrass, tall fescue, perennial rye, fine fescue, bermudagrass, zoysia, centipede and bahiagrass |
|---|---|
| Rate range | 0.4 lb per 1,000 ft² for centipede to 7 lb for tall fescue and bahiagrass, each editable to the bag's own tag |
| Why the rates differ | Seed count per pound: 175,000 for bahiagrass, 227,000 for tall fescue, 2,200,000 for Kentucky bluegrass |
| Overseeding | Half the new-lawn rate — 3 lb against 6 for a cool-season blend — applied automatically by the job selector |
| Germination windows | 5 to 7 days for perennial ryegrass, 14 to 21 for Kentucky bluegrass, 21 to 28 for bahiagrass |
| Bag sizes | 3, 5, 7, 10, 20, 25 and 50 lb, with the leftover in the last bag reported rather than rounded away |
| Starter fertilizer | 1 lb of nitrogen per 1,000 ft², converted through the bag's analysis: 5.6 lb of an 18% product, 8.3 lb of a 12% |
| Nothing leaves the page | Species, rates, areas and any prices you enter are held in the tab and gone when it closes |
Frequently asked questions
How many pounds of grass seed do I need per 1,000 square feet?
Between 0.4 lb and 8 lb, and which end you are at is decided entirely by the species. Centipede goes down at a quarter to half a pound, Kentucky bluegrass at 2 to 3, perennial ryegrass at 5 to 7, tall fescue at 6 to 8 and bahiagrass anywhere from 5 to 10. The spread is not a difference in how much grass you get: it is a difference in what a pound of seed contains. Sowing a fescue rate of bluegrass puts roughly ten times the intended number of seedlings on the ground, and sowing a bluegrass rate of fescue leaves gaps that fill with whatever germinates next.
Why is overseeding half the rate of a new lawn?
Because most of the lawn is already covered, and the seed you add is competing against established plants rather than filling empty ground. A thin lawn is not bare ground with grass on it — every seedling that lands there is starting under an existing canopy, in soil already full of roots, and the ones that survive are the ones that found a genuine gap. Doubling to a new-lawn rate does not fill more gaps, it just puts more seed where there is nowhere to go. The exception is a lawn that is more bare than grass, which is a renovation: strip it or kill it off and sow it as new ground at the full rate.
Will more seed give me a thicker lawn?
No, and past about one and a half times the published rate it gives you a worse one. Grass seedlings compete with each other exactly as they compete with weeds, so an over-sown stand comes up shoulder to shoulder, stretches for light, roots shallowly and then thins itself out through the first hot spell — leaving a lawn that is patchier than a correctly sown one and less able to survive a drought. The dense wet canopy is also where damping-off starts, and a seedling stand lost to Pythium in the first fortnight is lost entirely. Density in a lawn comes from tillering over the first two seasons, which is a function of mowing height, feeding and water, not of how much seed went into the spreader.
How much starter fertilizer goes down with the seed?
Enough product to put 1 lb of actual nitrogen on every 1,000 square feet, which for an 18-24-12 starter is 5.6 lb of the bag and for a 12% analysis is 8.3 lb. The rate is written in nitrogen rather than in bag weight because the same 1 lb comes from very different amounts of product, and reading the number off the front of the bag instead of dividing by the analysis is the standard way to double or halve a feed by accident. Worth knowing before you buy: several states restrict phosphorus on established lawns, with new seeding as the named exception, so the high middle number that makes a starter a starter is legal here and often not legal on the same lawn next spring.
Can I use a crabgrass preventer when I seed?
Not a normal one. Pre-emergent herbicides work by stopping seeds germinating, and they have no way to tell a crabgrass seed from the fescue you just paid for — a spring application typically holds the soil hostile to germination for 8 to 12 weeks, which is the entire window you were sowing into. The two products that are formulated to allow it are siduron and mesotrione, both labeled for use at seeding. Otherwise the sequence is one or the other: seed in fall and preventer the following spring, or preventer in spring and seed in the fall after it has broken down.
When is the right time to sow?
Late summer into early fall for cool-season grasses, and late spring for warm-season ones. The cool-season window works because the soil is still warm enough for fast germination while the air is cooling, the weed pressure that dominates spring seeding has passed, and the seedlings get an autumn and a spring to root before their first summer. Warm-season seed is the opposite: bermudagrass, zoysia and centipede want soil at 65 °F and rising, so they go down after the last frost and into early summer. Seeding at the wrong end of the year is the most common reason a correctly measured bag of seed produces nothing.
Why does the coverage on the bag not match this calculator?
Because most bags print their coverage at the overseeding rate, which is half the new-lawn rate. A bag stating that it covers 5,000 square feet will genuinely cover 5,000 of thin existing lawn and about 2,500 of bare soil, and the small print usually says so on the back in a place nobody reads in the aisle. This page reports what one bag of your chosen size covers at the rate you are actually using, which is the number to check the bag against — if it disagrees by roughly a factor of two, that is the reason.
About seeding rates, seed counts and why more is worse
Every seeding rate in the turf literature is written as pounds per 1,000 square feet, and every one of them belongs to a named species. That pairing is doing more work than it looks. Weight is simply how seed is sold; what lands on the ground is a number of seeds per square inch, and seed size varies across lawn grasses by more than a factor of ten. Kentucky bluegrass runs about 2.2 million seeds to the pound, fine fescue around 500,000, perennial ryegrass and tall fescue about 230,000 apiece, and bahiagrass fewer still. So the two-and-a-half pounds of bluegrass and the seven pounds of tall fescue that cover the same 1,000 square feet are not a disagreement about how much grass is wanted — they are the same intent expressed in a unit that happens to weigh different amounts. This page prints the seeds per square inch alongside the pounds for exactly that reason: it is the only figure on which two species can be compared, and it is what makes an unfamiliar rate on a bag either sensible or obviously wrong.
The corollary is the part that costs people a lawn. Adding seed beyond the rate does not add grass, it adds competition — and the competitor is the rest of your own seed. A heavily over-sown stand germinates as a mat of seedlings fighting for the same light, water and root space; they stretch, they root shallowly, and the stand thins itself out through the first dry fortnight into something patchier than a correctly sown lawn would have been. The wet, airless canopy is also ideal for damping-off, which takes seedlings faster than anything else will. Density in an established lawn comes from tillering over two seasons under a sensible mowing height, not from the spreader setting, so the useful place to spend extra effort is the seedbed: level ground, real contact between seed and soil, and water kept on it until germination. Where that seedbed needs building rather than raking, the compost calculator sizes the amendment and the raised bed soil calculator handles the ground that is being contained rather than sown.
Two practical notes that most calculators leave out. The first is timing, which decides more outcomes than the rate does: cool-season grasses go down in late summer and early fall into warm soil and cooling air, warm-season grasses after the last frost once the soil holds 65 °F, and seed sown at the wrong end of the year fails no matter how carefully it was measured. The second is what else is going on that season. A pre-emergent crabgrass product makes the soil hostile to germination for two to three months and cannot distinguish your seed from a weed’s; grass running up to a salt-chlorinated pool takes the splash-out along that edge, and the salinity a cell needs to keep working is set on the pool salt calculator; and the bed edges you mulch in the same weekend come off the mulch calculator. Where waiting out a germination window is not an option — a house going on the market, a yard churned by builders — the same ground can be bought finished by the pallet on the sod calculator, at perhaps ten times the material cost and a day instead of a season.
Where the seeding numbers are worked out
Every number on this page is worked out by JavaScript running in the tab you are reading it in. Nothing you type — measurements, quantities, the prices your supplier quoted you — is uploaded, logged or kept, which is also why the calculators carry on working on a site with no signal.
One consequence worth stating plainly: because nothing is saved, a rate you edited away from the species default is not remembered between visits. That is the trade for a page that holds no account and writes nothing down — set it again, or keep the copied materials list.