Grass Seed Calculator

The Grass Seed Calculator tells you exactly how much grass seed you need for your lawn, based on your lawn area, the grass type, and whether you are seeding a new lawn or overseeding an existing one. It converts your measurement into pounds of seed, rounds it up into whole bags, shows how much seed is left over, and can estimate your cost — all with a visual comparison of how densely new lawns and overseeding are sown.

How Much Grass Seed Do I Need?

Grass seed is applied at a seeding rate measured in pounds per 1,000 square feet. The amount you need depends on two things: the size of your lawn and the recommended rate for your grass type. The formula is simple:

For example, a 5,000 sq ft new lawn of tall fescue at 8 lb per 1,000 sq ft needs \( \frac{5{,}000}{1{,}000} \times 8 = 40 \) lb of seed. The same lawn overseeded uses roughly half that, about 20 lb.

Grass Seed Rate Chart (lb per 1,000 sq ft)

These are typical cooperative-extension seeding rates used in this calculator. Overseeding rates are roughly half the new-lawn rates because established turf already covers most of the soil.

New Lawn vs Overseeding: What is the Difference?

Seeding a new lawn means establishing turf on bare or nearly bare soil, so you need enough seed for full ground coverage. Overseeding means spreading seed over an existing lawn to thicken it, repair thin patches, or introduce a new grass. Because the old turf already occupies much of the ground, overseeding uses about half the seed of a new lawn. Using the new-lawn rate to overseed wastes seed and forces seedlings to compete; using the overseed rate on bare soil leaves a thin, patchy result.

How to Measure Your Lawn Area

• Rectangular lawns: multiply length by width. A 60 ft by 40 ft yard is 2,400 sq ft.
• Irregular lawns: divide the space into rectangles and triangles, calculate each piece, then add them up.
• Circles: area is \( \pi r^2 \), where \( r \) is the radius.
• Subtract non-lawn areas such as the house, driveway, patio, and flower beds so you do not over-buy.

This calculator accepts either a total area (in square feet, square meters, square yards, or acres) or a simple length × width in feet, meters, or yards.

Tips for Better Seeding Results

How to Use This Calculator

1. Choose your grass type and scenario: Pick your grass and whether you are seeding a new lawn or overseeding.
2. Enter your lawn area: Type a total area in your preferred unit, or switch to length × width and enter the dimensions.
3. Set bag size and optional price: Choose the bag size you plan to buy, and add a price per bag for a cost estimate.
4. Click Calculate: See the pounds of seed needed, number of bags, leftover seed, a seeding-rate gauge, and a step-by-step breakdown.

Frequently Asked Questions

How much grass seed do I need per square foot?

Grass seed is measured in pounds per 1,000 square feet, not per single square foot. Typical new-lawn rates range from about 0.4 lb per 1,000 sq ft for centipedegrass to 8 lb per 1,000 sq ft for tall fescue. To find your total, divide your lawn area by 1,000 and multiply by the seeding rate for your grass type.

How much grass seed do I need for overseeding?

Overseeding an established lawn usually uses about half the seed of a new lawn, because existing turf already covers most of the ground. For example, tall fescue is sown at about 8 lb per 1,000 sq ft for a new lawn but only about 4 lb per 1,000 sq ft when overseeding.

How many pounds of grass seed are in a bag?

Grass seed bags commonly come in 3, 5, 7, 10, 20, 25, and 50 pound sizes. This calculator lets you pick your bag size and then rounds up to the number of whole bags you need, showing how much seed is left over for touch-ups.

What is the best time to plant grass seed?

Cool-season grasses such as tall fescue, Kentucky bluegrass, and ryegrass are best sown in early fall or early spring. Warm-season grasses such as Bermudagrass, zoysiagrass, and centipedegrass are best sown in late spring to early summer once the soil is reliably warm.

Is it bad to use too much grass seed?

Yes. Over-seeding beyond the recommended rate makes seedlings compete for water, light, and nutrients, which leads to weak, thin, disease-prone turf. Staying close to the recommended pounds per 1,000 square feet gives the strongest, most even lawn.

How do I measure my lawn area for grass seed?

For a rectangular lawn, multiply length by width. For irregular lawns, break the area into rectangles and triangles, calculate each, and add them up. This calculator accepts either a total area or a simple length times width in feet, meters, or yards.

Additional Resources

• Lawn - Wikipedia