Grass Seed Calculator: How Much Grass Seed Do I Need?
Enter the lawn area and whether you are starting from bare soil or thickening what is there. The rate matters more than anything else here — seeding rates vary by a factor of three between species, so the default is a starting point you should replace with the figure on your bag.
Lawn area and seeding rate
Measure the grass only. The rate is on your seed bag — use it.
Seeding rates vary by a factor of three between species, and the right rate for your seed is printed on the bag. Treat the default as a starting point for a fescue or ryegrass mix, not as a recommendation.
How much grass seed do I need?
Seeding rates are quoted in pounds per thousand square feet, so the arithmetic is simple: measure the lawn, divide by a thousand, multiply by the rate. Everything that makes this hard is in choosing the rate.
Overseeding an existing lawn takes roughly half the rate of a new one, because the established grass is already doing most of the work. More is not better: seed sown too thickly competes with itself and thins out.
New lawn or overseeding?
| Mode | Default rate | When |
|---|---|---|
| New lawn | 6 lb / 1,000 sq ft | Bare soil, or a full renovation |
| Overseeding | 3 lb / 1,000 sq ft | Thickening a lawn that is already there |
Rates by species
This is where the number really comes from. Bluegrass seed is tiny and goes a long way; tall fescue seed is large and needs several times the weight for the same coverage. Using one rate for the other is how people end up with a bare lawn or a wasted bag.
| Species | New lawn | Overseeding |
|---|---|---|
| Kentucky bluegrass | 2.5 lb / 1,000 sq ft | 1.5 lb / 1,000 sq ft |
| Perennial ryegrass | 4.5 lb / 1,000 sq ft | 2.5 lb / 1,000 sq ft |
| Tall fescue | 6 lb / 1,000 sq ft | 3 lb / 1,000 sq ft |
| Fine fescue | 4.5 lb / 1,000 sq ft | 2.5 lb / 1,000 sq ft |
Typical figures for planning. The rate printed on your bag is the one to use.
How to measure a lawn
Beds, paths and the patio are not being seeded.
Add each as its own area. They are summed before the rate is applied.
It will be there, usually as pounds per 1,000 square feet for both new lawns and overseeding.
Common mistakes
- Using a bluegrass rate for a tall fescue seed, or the reverse.
- Sowing at the new-lawn rate when overseeding, which wastes seed and thins the result.
- Sowing more than the rate in the hope of a thicker lawn.
- Measuring the whole garden instead of the grass.
Would sod be faster?
For an instant lawn, price the turf against the seed.
Open the Sod Calculator →