Measure the lawn in square feet, read the rate on the bag, and divide. For a new tall fescue lawn that is usually six to ten pounds per thousand square feet; for overseeding an existing one it is roughly half that. A 25 lb bag of Jonathan Green Black Beauty Tall Fescue therefore covers a few thousand square feet of new lawn or a good deal more as an overseed, and a 5.6 lb bag like the Scotts Turf Builder Tall Fescue Mixis a patch-and-touch-up quantity rather than a whole-lawn one. Whatever the number, you need a spreader that holds a rate — the Scotts EdgeGuard DLX is the broadcast spreader most of these rates assume.
Two things make this harder than it should be. The first is that rates vary by species: fine, light seed like bluegrass goes much further per pound than big tall fescue seed, so the number is never one number. The second is coating — coated seed has material added around each seed for moisture retention, so part of the bag weight is not seed. Both of these are why the figure printed on your specific bag beats any rule of thumb, including ours.
We have not weighed anything out. The rates below are what the labels and standard turfgrass seeding practice publish; the arithmetic is arithmetic — see how we pick. Prices are live with an “as of” date.
Step one: get the square footage, properly
Everything depends on this number and most people guess it badly. Pace it out — a normal adult stride is close to three feet, so count paces and multiply by three to get feet.
A rectangle: length times width.
An L-shape or a lawn with a patio in it: break it into rectangles, work out each, add them up. Subtract the house, the drive, the beds and the pool. You are seeding grass, not the footprint of the property.
A circle: radius times radius times 3.14.
A genuinely irregular lawn: treat it as the rectangle that roughly contains it and subtract a quarter. It is close enough, and a satellite measuring tool on a mapping site will get you closer in two minutes.
Write the number down somewhere permanent. Every fertilizer bag, every pre-emergent, every weed product on this site is rated per thousand square feet, so you will use it again every time you buy anything — starting with the fertilizer schedule.
Step two: the rate
| Species | New lawn, per 1,000 sq ft | Overseeding, per 1,000 sq ft |
|---|
| Turf-type tall fescue | 6 to 10 lb | 3 to 5 lb |
| Fine fescue | 4 to 5 lb | 2 to 3 lb |
| Kentucky bluegrass | 2 to 3 lb | 1 to 2 lb |
| Perennial ryegrass | 6 to 9 lb | 3 to 5 lb |
| Bermudagrass (hulled) | 1 to 2 lb | 0.5 to 1 lb |
These are the standard published ranges for each species, and your bag's own figure wins wherever it differs — particularly on coated products, which state lower coverage per pound because some of the weight is coating. Bluegrass seed is tiny, which is why its rate looks implausibly low next to tall fescue; it is seeds per square inch that matters, not pounds.
Step three: the arithmetic, worked
A 5,000 sq ft new tall fescue lawn at 8 lb per 1,000: 5 times 8 = 40 lb. Two 25 lb bags, with some left for the inevitable thin strip.
The same lawn overseeded at 4 lb per 1,000: 20 lb. One 25 lb bag covers it comfortably.
A 2,000 sq ft shaded area in fine fescue at 4.5 lb per 1,000: 9 lb. A 10 lb bag.
A 400 sq ft bare patch at 8 lb per 1,000: about 3.2 lb. A 5.6 lb bag, and the rest goes in the shed for next spring.
Buy slightly over rather than slightly under. Running out two thirds of the way across a lawn means a visible seam for a season, and stored seed keeps for a year or two in a cool, dry, sealed container.
Why more seed gives a worse lawn
This is the counterintuitive part and it is worth being clear about. Doubling the rate does not double the lawn. It produces several times the number of seedlings in the same square inch, all competing for the same light, water and nutrients, and the result is a thick flush of weak, spindly grass with shallow roots that thins out under the first real stress of summer.
Dense sowing also raises disease pressure in seedling turf, because the canopy stays damp. And it wastes money twice: once on seed you did not need, and again on the overseeding you end up doing when the stand thins.
Under-seeding has the opposite failure: thin cover, visible soil and an open invitation to weeds. The published range exists because it is the band where neither of those happens.
The spreader is part of the rate
A rate you cannot apply evenly is a number on paper. Two habits make a real difference, and both are free.
Halve the setting and go twice, at right angles. Two light passes crossing each other cover far more evenly than one heavy pass, and they hide the drift at the edge of each sweep.
Keep a steady walking pace and shut the hopper at turns. A broadcast spreader meters by ground speed, so slowing down doubles your rate without you noticing.
Which machine matters mainly for edge control — a spreader that throws seed into beds and onto the drive wastes it twice. The broadcast spreader rankings cover that, and broadcast vs drop explains which type suits your lawn. For a small area, a hand spreader is fine; a hand-thrown application is not, because nobody throws evenly.
Then do not waste it
Seed is the cheap part of seeding. Getting it to germinate is the rest, and the rate is irrelevant if the seed is lying on thatch or dries out on day four. Mow short and collect first, aerate if you can, feed with a starter fertilizer rather than a normal bag, and keep the top half inch of soil damp for two to three weeks. The full sequence is in how to grow grass from seed and, for an existing lawn, how to reseed a lawn.
One more thing is worth more than the rate: the date. Sowing the right quantity into the wrong soil temperature wastes all of it, and the windows are narrower than most people think — see when to plant grass seed.
