Our free overseeding calculator tells you how many pounds of grass seed your existing lawn needs. Pick your grass type and lawn condition — thin, patchy, or nearly bare — and get an instant answer. (Starting a brand-new lawn? Use our grass seed calculator instead.)
👤 Who is this for: homeowners with thin lawns & fall renovation DIYers.
How to use
- Enter your lawn length and width in feet.
- Choose your grass type and describe your lawn’s condition.
- Hit Calculate Overseeding.
Overseeding formula
Seed (lbs) = (Lawn sq ft ÷ 1,000) × seeding rate × condition multiplier. Condition multipliers: thin lawn 1×, very thin/patchy 1.5×, nearly bare 2×.
Example: a 5,000 sq ft tall fescue lawn in thin condition → (5,000 ÷ 1,000) × 2 × 1 = 10 lbs of seed.
Overseeding rates by grass type
| Grass type | Lbs per 1,000 sq ft |
|---|---|
| Bermuda | 1.5 |
| Tall fescue | 2 |
| Kentucky bluegrass | 1 |
| Perennial ryegrass | 2.5 |
| Zoysia | 1 |
📝 Real Project Example
5,000 sq ft thin tall-fescue lawn, fall overseed:
- Seed needed: 5 × 4 = 20 lbs (half the 7-lb new-lawn rate, rounded)
- Prep: mow short, aerate, then seed — seed-to-soil contact decides everything
- Water: 2–4 light waterings daily for 2 weeks; taper as seedlings establish
- Cost check: 20 lbs tall fescue at ~$3/lb = ~$60
Overseed when nights cool (late August to mid-September for cool-season grass). Spring overseeding fights crabgrass and summer heat — fall wins.
Tips
- Mow your existing grass short before overseeding so seed reaches the soil.
- Aerate first if you can — it doubles germination.
- Fall is the best time to overseed cool-season grasses; late spring for warm-season grasses.
📚 Sources & Methodology
How we calculate. Step 1: lawn area in square feet. Step 2: seed needed = (area ÷ 1,000) × overseeding rate for your grass (roughly half the new-lawn rate — e.g. tall fescue ~4 lbs, Kentucky bluegrass 1–2 lbs per 1,000 sq ft). Add 10% for thin/bare patches.
Cross-checked. Our half-rate rule and species rates match extension and industry overseeding guides; always follow the rate on your specific seed bag.
Sources:
- SunSeeker Elite — How Much Seed to Overseed Lawn (species overseeding-rate table)
- University of Nebraska Extension — Get Ready for Lawn Seeding (half rate into existing lawns)
Last updated: October 2026.
Frequently asked questions
Related calculators: Grass Seed Calculator, Fertilizer Calculator