Grass Seed Calculator

How it works

Grass seed is applied at a rate given in pounds per 1,000 square feet. The rate depends on the species and on whether you are seeding bare soil or overseeding an existing lawn: a new lawn needs roughly twice the seed of an overseed because there is no existing grass to fill in.

Length times width gives the lawn area in square feet. Dividing by 1,000 and multiplying by the rate gives the pounds of seed. Dividing by the bag size and rounding up gives the bags to buy.

Formula

area   = length × width
pounds = (area ÷ 1,000) × seed rate
bags   = pounds ÷ bag size, rounded up

Example

A 50 ft × 40 ft lawn is 2,000 sq ft. At 4 lb per 1,000 sq ft that needs 2 × 4 = 8.0 lb of seed, which is one 10 lb bag.

Overseeding the same lawn with tall fescue at 3 lb per 1,000 sq ft needs 2 × 3 = 6.0 lb, still one 10 lb bag.

Assumptions and limitations

• The lawn is a rectangle. For an irregular lawn, add up the rectangles it breaks into and enter the total as the length with a width of 1.
• Seeding rates vary by species, cultivar, blend and brand, and between a new lawn and an overseed. The rates in the help text are typical published ranges; the rate on your bag is the one to use.
• The rate assumes seed spread evenly with a spreader at the setting the bag recommends. Spreading by hand usually uses more.
• Subtract beds, paths and driveways from the area before entering it; the calculator does not know what is lawn.
• Seeding too heavily wastes seed and makes seedlings crowd each other out; seeding too thinly leaves gaps that weeds fill. Stay within the rate range for your grass.

Frequently asked questions