Lawn Seed Calculator
Grass seed is sold and dosed by weight per 1,000 square feet, with the right rate set by the species you are sowing and whether you are establishing a new lawn or overseeding an existing one. Turning that rate into a shopping list is simple arithmetic once you know your area. Enter your lawn area in square feet and the seeding rate from your extension service or seed label, and this calculator returns the total pounds of seed, the bags needed, and the effective coverage of one bag so you can plan a delivery or store run.
Lawn seed formula
Area units = area / 1,000
Seed needed = seeding rate * area units
Bags needed = seed needed / bag weight
Coverage of one bag = (bag weight / seeding rate) * 1,000
The seeding rate already accounts for the species and whether you are seeding new ground or overseeding. The calculator simply scales it to your area.
Seeding context
- New seeding uses the full rate; overseeding an existing lawn typically uses about half.
- Cool-season grasses are best sown in early fall; warm-season grasses in late spring to early summer.
- Your state cooperative extension service publishes seeding rates by species and region.
- Over-seeding wastes seed and leads to crowded, disease-prone seedlings; stick to the recommended rate.
- Good seed-to-soil contact and consistent moisture matter as much as the right quantity.
Lawn seed calculator: frequently asked questions
How much grass seed do I need?
Seed is quoted as pounds per 1,000 square feet. Multiply your seeding rate by your lawn area divided by 1,000 to get the pounds of seed. For example, a rate of 5 pounds per 1,000 square feet over a 4,000 square foot lawn needs 5 times 4, which is 20 pounds of seed.
Why is the seeding rate something I enter?
The right rate depends on the grass species: fine fescues, tall fescue, Kentucky bluegrass, and ryegrass all differ, and overseeding uses about half the rate of new seeding. Your state cooperative extension service publishes species-specific rates. Because there is no single correct figure, this calculator takes the rate as an input.
What is the difference between seeding and overseeding?
New seeding establishes a lawn on bare soil and uses the full rate. Overseeding adds seed to an existing thin lawn to thicken it and typically uses roughly half the new-seeding rate. Enter the rate that matches your task; the calculator simply multiplies it by your area.
How do I find my lawn area?
Measure the length and width of each rectangular section in feet, multiply to get the area of each, and add them up. For irregular shapes, break the lawn into rectangles and triangles. Enter the total square footage and the calculator does the rest.
How do I convert the seed weight to bags?
Divide the total pounds of seed by the bag weight. If you need 20 pounds and a bag holds 7 pounds, that is about 2.9 bags, so you would buy three. The calculator shows the bag count when you enter a bag weight.
Official sources
- USDA Natural Resources Conservation Service: Seeding rate guidance.
- USDA PLANTS Database: Grass species reference.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.