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Lawn Overseed Calculator

Calculate grass seed for your lawn

Seed Needed

25 lbs

5 lb Bags

5

Fertilizer

25 lbs

Seed Needed

25

pounds

5 lb Bags

5

Starter Fertilizer

25 lbs

New vs Overseed Comparison

New Lawn Rate40 lbs (8 bags)
Overseed Rate25 lbs (5 bags)
Starter Fertilizer2 bag(s) of 20 lb

Seed & Cost Comparison

New Lawn Seed40.0 lbs
Overseed Only25.0 lbs
Starter Fertilizer40.0 lbs

Tips for Tall Fescue

Best Time to Seed

Fall (late August to mid-October) or early spring

Watering

Keep soil moist (not soggy) until germination. Water lightly 2-3 times daily.

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What You'll Need

Scotts Turf Builder Grass Seed Sun and Shade Mix - Grass Seed Plus Lawn Fertilizer and Soil Improver, Covers Up to 2,240 sq. ft., 5.6 lb.

Scotts Turf Builder Grass Seed Sun and Shade Mix - Grass Seed Plus Lawn Fertilizer and Soil Improver, Covers Up to 2,240 sq. ft., 5.6 lb.

$29.974.2
View on Amazon
Scotts Turf Builder Starter Food for New Grass, 15 lb. - Lawn Fertilizer for Newly Planted Grass, Also Great for Sod and Grass Plugs - Covers 5,000 sq. ft.

Scotts Turf Builder Starter Food for New Grass, 15 lb. - Lawn Fertilizer for Newly Planted Grass, Also Great for Sod and Grass Plugs - Covers 5,000 sq. ft.

$29.984.5
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Scotts Turf Builder EdgeGuard DLX Broadcast Spreader - Spreader for Lawn Fertilizer, Weed & Insect Control, Grass Seed, and Ice Melt, Holds Up to 15,000 sq. ft. of Product

Scotts Turf Builder EdgeGuard DLX Broadcast Spreader - Spreader for Lawn Fertilizer, Weed & Insect Control, Grass Seed, and Ice Melt, Holds Up to 15,000 sq. ft. of Product

$99.974.4
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Scotts Whirl Hand-Powered Spreader - for Grass Seed, Lawn Fertilizers, Salt, and Ice Melt, Handheld Spreader Holds up to 1,500 sq. ft. of Product

Scotts Whirl Hand-Powered Spreader - for Grass Seed, Lawn Fertilizers, Salt, and Ice Melt, Handheld Spreader Holds up to 1,500 sq. ft. of Product

$24.994.7
View on Amazon
Scotts Turf Builder Grass Seed Sun and Shade Mix - Grass Seed Plus Lawn Fertilizer and Soil Improver, Covers Up to 2,240 sq. ft., 5.6 lb.

Scotts Turf Builder Grass Seed Sun and Shade Mix - Grass Seed Plus Lawn Fertilizer and Soil Improver, Covers Up to 2,240 sq. ft., 5.6 lb.

$29.974.2
View on Amazon
Scotts Turf Builder Starter Food for New Grass, 15 lb. - Lawn Fertilizer for Newly Planted Grass, Also Great for Sod and Grass Plugs - Covers 5,000 sq. ft.

Scotts Turf Builder Starter Food for New Grass, 15 lb. - Lawn Fertilizer for Newly Planted Grass, Also Great for Sod and Grass Plugs - Covers 5,000 sq. ft.

$29.984.5
View on Amazon
Scotts Turf Builder EdgeGuard DLX Broadcast Spreader - Spreader for Lawn Fertilizer, Weed & Insect Control, Grass Seed, and Ice Melt, Holds Up to 15,000 sq. ft. of Product

Scotts Turf Builder EdgeGuard DLX Broadcast Spreader - Spreader for Lawn Fertilizer, Weed & Insect Control, Grass Seed, and Ice Melt, Holds Up to 15,000 sq. ft. of Product

$99.974.4
View on Amazon
Scotts Whirl Hand-Powered Spreader - for Grass Seed, Lawn Fertilizers, Salt, and Ice Melt, Handheld Spreader Holds up to 1,500 sq. ft. of Product

Scotts Whirl Hand-Powered Spreader - for Grass Seed, Lawn Fertilizers, Salt, and Ice Melt, Handheld Spreader Holds up to 1,500 sq. ft. of Product

$24.994.7
View on Amazon

As an Amazon Associate, we earn from qualifying purchases.

Example Calculations

15,000 sq ft Lawn with Tall Fescue

Inputs

Lawn Area5,000 sq ft
Grass TypeTall Fescue

Result

Seed (New Lawn)40.0 lbs (8 bags)
Seed (Overseed)25.0 lbs (5 bags)
Starter Fertilizer25.0 lbs (2 bags)

New lawn: (5000 / 1000) x 8 = 40.0 lbs, ceil(40/5) = 8 bags. Overseed: (5000 / 1000) x 5 = 25.0 lbs, ceil(25/5) = 5 bags. Fertilizer: 5000 / 200 = 25.0 lbs, ceil(25/20) = 2 bags.

23,000 sq ft Lawn with Kentucky Bluegrass

Inputs

Lawn Area3,000 sq ft
Grass TypeKentucky Bluegrass

Result

Seed (New Lawn)9.0 lbs (2 bags)
Seed (Overseed)6.0 lbs (2 bags)
Starter Fertilizer15.0 lbs (1 bag)

New lawn: (3000 / 1000) x 3 = 9.0 lbs, ceil(9/5) = 2 bags. Overseed: (3000 / 1000) x 2 = 6.0 lbs, ceil(6/5) = 2 bags. Fertilizer: 3000 / 200 = 15.0 lbs, ceil(15/20) = 1 bag.

Frequently Asked Questions

Q

How much grass seed do I need per square foot?

For new lawns: Kentucky bluegrass needs 3 lbs/1000 sq ft, while tall fescue and perennial rye need 8 lbs/1000 sq ft. For overseeding, use about 60-70% of new lawn rates.

  • Kentucky bluegrass seeds are tiny—fewer pounds cover more area vs. fescue
  • Overseed rates are typically 50–70% of new-lawn seeding rates
  • Seed mixes use blended rates—check the label for individual species percentages
  • Buy certified seed with 85%+ germination rate (printed on the bag tag)
Grass TypeNew Lawn (lbs/1,000 ft²)Overseed (lbs/1,000 ft²)Seeds per lb
Kentucky Bluegrass2–31.5–22.2 million
Tall Fescue6–84–5230,000
Perennial Ryegrass6–84–5230,000
Bermudagrass1–20.5–11.8 million
Fine Fescue4–53–4580,000
Q

When is the best time to overseed a lawn?

Fall is ideal for cool-season grasses (late August to mid-October). For warm-season grasses like Bermuda, overseed in late spring when soil reaches 65-70°F.

  • Cool-season grasses: seed August 15–October 15 for 6–8 weeks of growth before frost
  • Warm-season grasses: seed late May–June when soil temperature stays above 65°F
  • Soil temperature matters more than air temperature—check with a probe thermometer
  • Avoid seeding in summer—heat stress kills seedlings before they establish
  • Spring overseeding of cool-season grass works but competes with crabgrass germination
Q

Should I use starter fertilizer when seeding?

Yes, starter fertilizer promotes root development. Apply at seeding time at about 1 lb of actual phosphorus per 1000 sq ft. Avoid high-nitrogen fertilizers initially.

  • Starter fertilizers like 10-18-10 or 18-24-6 are designed for new seedings
  • Apply at seeding time—phosphorus needs to be near the seed for root uptake
  • A 20 lb bag of 10-18-10 covers roughly 4,000 sq ft of new lawn
  • Wait 4–6 weeks after germination before applying regular nitrogen fertilizer
  • Some states restrict phosphorus in fertilizer—check local regulations first
Q

How long until grass seed germinates?

Perennial rye: 5-10 days. Tall fescue: 7-14 days. Kentucky bluegrass: 14-21 days. Bermuda: 7-14 days. Keep soil consistently moist during germination.

  • Water 2–3 times daily for 5–10 minutes to keep the top 1 inch moist until germination
  • After seedlings emerge, reduce to once daily watering with deeper soaking
  • Mow for the first time when grass reaches 3–4 inches—never cut more than 1/3 of the blade
  • Avoid foot traffic on new grass for at least 6–8 weeks after germination
Grass TypeGermination (days)First Mow (weeks)Full Establishment
Perennial Ryegrass5–103–46–8 weeks
Tall Fescue7–144–58–10 weeks
Kentucky Bluegrass14–215–610–14 weeks
Bermudagrass7–143–48–12 weeks

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Last Updated: Jul 2, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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