Enter the lawn size and the seeding rate from your seed bag to see how many pounds of grass seed to buy.
How to use the grass seed calculator
- Enter the size of the area you are seeding. Subtract beds, paths and the driveway.
- Choose whether this is a new lawn or an overseeding — overseeding uses about half the rate.
- Enter the seeding rate from the bag, in pounds per 1,000 square feet. Rates vary a lot between species.
- Enter the bag size and price to see how many bags to buy and what it costs.
Formulas
Pounds = area (ft²) ÷ 1,000 × rate (lb per 1,000 ft²) Overseeding = pounds × 0.5 Bags = pounds ÷ bag size, rounded up
There is no single correct seeding rate. Fine-seeded grasses such as Kentucky bluegrass go down at a low rate because there are so many seeds per pound, while tall fescue and ryegrass need several times more. The rate printed on your bag is the one to use — it is matched to that blend.
Worked example: a 4,000 ft² lawn at 6 lb per 1,000 ft²
- Thousands of square feet: 4,000 ÷ 1,000 = 4.
- New lawn: 4 × 6 = 24 lb of seed.
- Overseeding instead: 24 × 0.5 = 12 lb.
- Bags of 10 lb: 24 ÷ 10 = 2.4, so buy 3 bags.
New lawn or overseeding
A new lawn is seeded onto bare, raked soil and needs full rate because nothing is growing yet. Overseeding goes into an existing lawn to thicken it, so roughly half the rate is enough — more than that just wastes seed, since the seedlings compete with established grass. Either way, seed makes contact with soil or it does not germinate.
Quick reference
| Lawn size | At 4 lb / 1,000 ft² | At 8 lb / 1,000 ft² |
|---|---|---|
| 1,000 ft² | 4 lb | 8 lb |
| 2,500 ft² | 10 lb | 20 lb |
| 5,000 ft² | 20 lb | 40 lb |
| 10,000 ft² | 40 lb | 80 lb |
| 1 acre (43,560 ft²) | 174 lb | 349 lb |
Halve these figures for overseeding.
Questions
How much grass seed do I need for 1,000 square feet?
It depends on the species. At 4 lb per 1,000 ft² you need 4 lb; at 8 lb per 1,000 ft² you need 8 lb. Use the rate printed on your seed bag rather than a general figure.
How much seed do I need per acre?
An acre is 43,560 ft², so 43.56 times the rate. At 6 lb per 1,000 ft² that is about 261 lb.
Can I use more seed to get a thicker lawn?
No. Overseeding past the recommended rate makes seedlings compete with each other for water and light, and the lawn comes in weaker, not thicker.
Do I need less seed when overseeding?
Yes, about half. The existing grass is already covering the ground, so the seed is only filling gaps.
How much grass seed do I need for half an acre?
Half an acre is 21,780 ft², so multiply your rate by 21.78. At 6 lb per 1,000 ft² that is about 131 lb for a new lawn, or about half that for overseeding.
Sources
- NIST Guide to the SI, Appendix B.8: Factors for units listed alphabetically, National Institute of Standards and Technology.
Used for: Exact inch, foot and gallon definitions and the metric conversions.