Lawn Area: The total square footage of the rectangular area you plan to seed. For irregular lawns, break into rectangles and add the areas together.
Coverage Rate: The pounds of seed per 1,000 sq ft for your chosen grass species and whether you are seeding a new lawn or overseeding an existing one. New lawns need roughly double the seed of overseeding.
Total Seed Needed: The total weight of grass seed for your entire lawn area at the recommended coverage rate.
Bags Needed: The number of standard 50-lb bags to purchase, rounded up. Buy one extra to fill in thin spots after germination.
Germination Time: Most lawn grass species germinate in 7–14 days under proper soil temperature and moisture conditions, though some varieties like Kentucky bluegrass may take closer to 21 days.
How This Calculator Works
You enter the lawn length and width in feet, pick a seed type, and choose new lawn or overseeding. The tool multiplies the area by the species-specific seeding rate per 1,000 sq ft, then divides by 50 to convert to standard bag count, rounding up. Overseeding rates are roughly half of new-lawn rates. It assumes standard purity and germination percentages and does not adjust for slope or shade.
Quick Questions
What is the difference between seeding a new lawn and overseeding?
A new lawn is bare soil that needs full seed coverage to establish turf from scratch. Overseeding is spreading seed over an existing lawn to fill thin spots and improve density. Overseeding uses about half the seed rate because established grass already covers much of the ground.
Does soil temperature matter for germination?
Yes, significantly. Cool-season grasses germinate best when soil temperatures are 50–65°F, while warm-season grasses prefer 65–70°F or higher. Seeding when the soil is too cold or too hot leads to poor germination and wasted seed.
Should I use a seed blend or a single species?
Blends (multiple species in one bag) generally perform better because they tolerate a wider range of conditions. A blend might include sun- and shade-tolerant species so the lawn fills in evenly. Single-species seed works well for specific conditions like full sun or a very uniform appearance.
How do I know if the seed quality is good?
Check the bag tag for weed seed percentage (should be under 0.5%), germination rate (typically 80–90%+), and purity. Higher purity and germination mean more of the seed you buy will actually grow into grass.