Grass seed is sold by weight but applied by area, so the whole job comes down to your lawn's square footage and a seeding rate in pounds per 1,000 square feet. Get those two numbers and the amount is simple.
Measure your lawn first
Multiply length × width for a rectangular lawn. For odd shapes, break the yard into rectangles, figure each, and add them up. Drop the total into the grass seed calculator and it returns the pounds to buy.
New lawn vs overseeding
The biggest factor is whether you are starting from bare ground or thickening an existing lawn. A brand-new seeding uses roughly double the rate of overseeding, because you need full coverage rather than just filling gaps.
Typical seeding rates by grass type
Rates below are pounds per 1,000 sq ft for new seeding — halve them for overseeding:
- Kentucky bluegrass: 2–3 lb
- Tall fescue: 6–8 lb
- Perennial ryegrass: 5–7 lb
- Fine fescue: 3–5 lb
Always check the bag — blends and coated seed vary.
Do the math
Say you have a 5,000 sq ft lawn and you are seeding new tall fescue at 7 lb per 1,000 sq ft: 5 × 7 ≈ 35 lb of seed. Overseeding the same lawn would take roughly half that. The calculator does this instantly once you enter your area.
A few tips
- Buy about 10% extra for bare patches and touch-ups.
- More is not better — over-seeding makes seedlings compete and thin out.
- Good seed-to-soil contact matters most; rake lightly and keep it moist. A thin layer of topsoil helps on bare spots.
Enter your lawn size in the grass seed calculator for the exact pounds, then plan feeding with the fertilizer calculator.