About the Grass Seed Calculator
This grass seed calculator estimates how many pounds of seed you need to establish a new lawn or overseed a thin one. Pick the grass type, choose new lawn or overseeding, and enter the area in square feet; the tool applies a typical seeding rate for that species and tells you how many bags to buy and what it will cost.
Seeding rates vary enormously because seed size varies: a pound of Kentucky bluegrass holds around ten times as many seeds as a pound of tall fescue, so fescue is sown at a much higher weight. Overseeding an existing lawn usually needs about half the new-lawn rate. The comparison table shows how much seed each common species would need for your area.
Rates used here are mid-range figures from typical extension and seed-label guidance. Always check the bag — blends and coated seed can carry different recommendations — and use the custom rate field to override when your label says otherwise.
With the default inputs, the seed needed is 16 lb. Change any value above to recalculate instantly.
How to use the grass seed calculator
- 1Measure the lawn area in square feet (length × width for each section).
- 2Choose your grass type — match the seed you already have for overseeding.
- 3Select new lawn or overseeding.
- 4Enter the bag size and price, or a custom rate from the seed label.
- 5Buy the number of bags shown and spread in two perpendicular passes.
Formula and method
Seeding rates are published in pounds per 1,000 sq ft. The calculator divides your area by 1,000 and multiplies by the rate for the chosen species and job type, then rounds bags up to whole bags. New-lawn rates aim for full coverage on bare soil; overseeding rates are roughly half, because existing turf already fills much of the space.
The built-in rates are mid-points of common ranges (for example tall fescue 6–10 lb and Kentucky bluegrass 2–3 lb per 1,000 sq ft for new lawns). Coated seed, blends and local conditions change the ideal rate, so a custom rate overrides the default.
- Area
- Lawn area in square feet
- Seeding rate
- Pounds of seed per 1,000 sq ft for the grass and job type
Worked examples
New 2,000 sq ft tall fescue lawn
Tall fescue is sown at about 8 lb per 1,000 sq ft on bare soil, so 2,000 sq ft needs 16 lb. That is two 10 lb bags, or $90 at $45 a bag.
Overseeding 5,000 sq ft of Kentucky bluegrass
Bluegrass seed is tiny, so overseeding needs only about 1.5 lb per 1,000 sq ft. Over 5,000 sq ft that is 7.5 lb — a single 10 lb bag.
10,000 sq ft new Bermuda lawn
Hulled Bermudagrass is seeded at about 1.5 lb per 1,000 sq ft, so 10,000 sq ft needs 15 lb — three 5 lb bags costing $120.
Frequently asked questions
How much grass seed do I need per 1,000 square feet?+
It depends on the species: roughly 6–10 lb for tall fescue or perennial ryegrass, 2–3 lb for Kentucky bluegrass, 1–2 lb for Bermuda or zoysia and under 1 lb for centipedegrass on a new lawn. Overseeding needs about half as much.
Can I put down too much grass seed?+
Yes. Seeding far above the recommended rate makes seedlings compete for light, water and nutrients, leading to weak, disease-prone turf. Stick close to the label rate.
When is the best time to plant grass seed?+
Sow cool-season grasses such as fescue, bluegrass and ryegrass in late summer to early fall, with spring as a second choice. Sow warm-season grasses such as Bermuda and zoysia in late spring to early summer when soil is above about 65°F.
How long does grass seed take to germinate?+
Perennial ryegrass can sprout in 5–10 days, tall fescue in 7–14 days, Bermuda in 10–30 days and Kentucky bluegrass in 14–30 days, provided the seedbed stays consistently moist.
Should I fertilize when seeding?+
A starter fertilizer at seeding helps establishment, especially on new lawns. Use the fertilizer calculator to convert the recommended nutrient rate into pounds of product.