Grass Seed Calculator
Work out how much grass seed you need. Enter your lawn size and pick new lawn or overseed to get the exact pounds of seed using the per-1000-sqft rate.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Grass Seed Calculator Works
This calculator tells you how many pounds of grass seed to buy for your lawn. Enter the lawn’s length and width in feet, then choose whether you are seeding a new lawn or overseeding an existing one. The tool multiplies your lawn area by the correct seeding rate and returns the total seed needed.
Seed bags and lawn-care guides almost always quote coverage per 1,000 square feet, so this calculator uses that same standard unit.
The Formula
Lawn area (sqft) = length × width Seed (lbs) = (area ÷ 1,000) × seeding rate
The seeding rate is the pounds of seed recommended per 1,000 sqft:
- New lawn: about 4–5 lb per 1,000 sqft
- Overseeding: about 2–3 lb per 1,000 sqft
Worked Example
For a lawn that is 50 ft long and 40 ft wide, starting a new lawn at 5 lb per 1,000 sqft:
- Area = 50 × 40 = 2,000 ft²
- Seed = (2,000 ÷ 1,000) × 5 = 2 × 5 = 10 lb
If you were overseeding the same lawn at 3 lb per 1,000 sqft:
- Seed = (2,000 ÷ 1,000) × 3 = 2 × 3 = 6 lb
The larger lawn area and the heavier new-lawn rate both push the seed requirement up.
Typical Seeding Rates by Grass Type
The right rate depends on the grass species. These are common values you will see on seed bags:
| Grass type | New lawn (lb / 1000 sqft) | Overseed (lb / 1000 sqft) |
|---|---|---|
| Kentucky bluegrass | 2–3 | 1–2 |
| Perennial ryegrass | 5–9 | 3–5 |
| Tall fescue | 6–9 | 3–5 |
| Fine fescue | 4–5 | 2–3 |
| Bermuda (hulled) | 1–2 | 0.5–1 |
Tips for Even Coverage
- Always trust the bag. The printed rate is calibrated to that exact seed blend; use it over any general chart.
- Split the seed in half. Spread one half walking north-south and the other east-west for uniform coverage and no stripes.
- Don’t over-apply. Crowded seedlings compete and thin out, so heavier is not better.
- Buy a little extra. Add about 5–10 percent to cover edges, refills and bare patches.
Calculating the right amount up front means you buy one correctly sized bag instead of running short halfway through, or paying for seed you never use.
Frequently asked questions
How much grass seed do I need per square foot?+
Seeding rates are quoted per 1,000 sqft. A new lawn typically needs 4–5 lb per 1,000 sqft and overseeding needs 2–3 lb per 1,000 sqft. Per single square foot that is roughly 0.004–0.005 lb for new lawns, which is why rates are always given per 1,000 sqft instead.
What is the difference between new lawn and overseed rates?+
A new lawn starts from bare soil and needs a heavier rate (about 4–5 lb per 1,000 sqft) to fully cover the ground. Overseeding adds seed to an existing lawn to thicken it, so it uses a lighter rate of about 2–3 lb per 1,000 sqft.
How do I measure my lawn area?+
Multiply the length by the width in feet for a rectangular lawn. For irregular shapes, break the lawn into rectangles and triangles, calculate each area and add them together. Subtract beds, paths and the house footprint that you are not seeding.
Does seeding rate change by grass type?+
Yes. Fine seeds like Kentucky bluegrass are seeded lighter (around 2–3 lb per 1,000 sqft for new lawns) while larger seeds like tall fescue or ryegrass go down heavier (5–9 lb per 1,000 sqft). Always check the bag, since the printed rate overrides general guidance.
What happens if I use too much grass seed?+
Over-seeding causes seedlings to compete for water, light and nutrients, leading to thin, weak grass and more disease. It also wastes money. Sticking close to the recommended per-1,000-sqft rate gives the densest, healthiest turf.