Grass Seed Calculator
How many pounds of grass seed your lawn needs from its size and the seeding rate.
How it works
area = length × width · seed (lb) = ⌈area ÷ 1,000 × rate⌉
Lawn area in square feet, divided by 1,000, gives the number of 1,000-sq-ft units, and multiplying by the seeding rate gives pounds of seed. The result is rounded up to the next whole pound since seed is sold in bags. Match the rate to the job — heavier for a new lawn, lighter for overseeding — and use the number on your specific seed bag when it differs from the defaults.
Worked example
A 50 × 40 ft lawn is 2,000 sq ft. At the standard new-lawn rate of 5 lb per 1,000 sq ft, that’s 2,000 ÷ 1,000 × 5 = 10 lb of seed.
Frequently asked questions
What’s the difference between new-lawn and overseeding rates?
Seeding a bare area from scratch uses the full rate (4–6 lb per 1,000 sq ft for most cool-season grasses) so the ground fills in. Overseeding thickens an existing lawn, so you use about half that — the established grass is already doing most of the covering.
Does the seed type change the rate?
Yes. Fine fescues and ryegrasses seed heavier, Kentucky bluegrass lighter, and warm-season grasses like Bermuda differ again. The bag’s label rate always wins over a general rule — enter it in the rate field.
When is the best time to seed?
For cool-season grasses, early fall is ideal — warm soil, cooler air and fewer weeds. Spring is the second-best window. Warm-season grasses go down in late spring to early summer once the soil has warmed.
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This calculator is for educational purposes. Double-check important results before acting on them.