Lawn Seeding Calculator
Calculate how much grass seed and starter fertilizer you need for any lawn size. Get bag counts and cost estimates for Kentucky Bluegrass, Tall Fescue, Bermuda, and more.
Enter the total area you plan to seed. If you are unsure, measure the length × width of each section and add them together.
Shopping List
New lawn · 5,000 sq ft · Kentucky Bluegrass
Grass Seed
Starter Fertilizer
Total Material Cost
$0.03 per sq ft
Seed costs based on typical retail prices per lb. Fertilizer estimate assumes a standard 5,000 sq ft starter bag at ~$30. Labor not included.
💡About this calculator▼
Getting the right amount of seed is one of the most common mistakes homeowners make when seeding a lawn. Too little and you end up with thin, patchy coverage. Too much wastes money and can actually crowd out germination.
This calculator gives you the exact pounds of grass seed you need, how many bags to buy, and the starter fertilizer required — all based on your grass type, lawn size, and whether you are starting fresh or overseeding an existing lawn.
The calculator uses published seeding rates (pounds of seed per 1,000 square feet) for each grass type, then multiplies by your lawn area to get total seed needed. It rounds up to whole bags so you always have enough. Starter fertilizer is sized at one standard bag per 5,000 square feet — the coverage rate on most major brands. Overseeding uses roughly half the seed rate of a new lawn since existing turf helps fill gaps.
📐How it's calculated▼
Seed needed (lbs) = (Lawn area ÷ 1,000) × seeding rate
Seeding rates used: - Kentucky Bluegrass: 2.5 lbs/1,000 sq ft (new), 1.5 lbs/1,000 sq ft (overseed) - Tall Fescue: 7 lbs/1,000 sq ft (new), 3.5 lbs/1,000 sq ft (overseed) - Perennial Ryegrass: 7 lbs/1,000 sq ft (new), 3.5 lbs/1,000 sq ft (overseed) - Fine Fescue: 4.5 lbs/1,000 sq ft (new), 2.5 lbs/1,000 sq ft (overseed) - Bermuda Grass: 1.5 lbs/1,000 sq ft (new), 0.75 lbs/1,000 sq ft (overseed) - Zoysia Grass: 1.5 lbs/1,000 sq ft (new), 0.75 lbs/1,000 sq ft (overseed)
Bags to buy = Seed needed ÷ bag size, rounded up to the nearest whole bag
Seed cost = Bags × bag size × price per lb (approximate retail pricing)
Starter fertilizer = Lawn area ÷ 5,000, rounded up to whole bags at ~$30/bag
Total material cost = Seed cost + fertilizer cost
📎Source: University Cooperative Extension seeding rate guidelines and seed manufacturer recommendations (Scotts, Jonathan Green, Pennington)
🔍Finding your inputs▼
Grass Type: Select the grass you are planting. If you are not sure, cool-season grasses (Kentucky Bluegrass, Tall Fescue, Ryegrass, Fine Fescue) are used in northern and transition zones. Warm-season grasses (Bermuda, Zoysia) are used in the South and Sun Belt. Check what your neighbors grow or ask your local extension office.
Seeding Type: Select New Lawn if you are seeding bare soil, a new construction area, or a section that has been stripped. Select Overseeding if you are thickening an existing thin or damaged lawn without removing existing turf.
Lawn Area: Enter the total area to be seeded in square feet. For irregular shapes, break the lawn into rectangles, calculate each (length × width), and add them together. You do not need to subtract areas like garden beds or trees — just estimate the grass zone.
⚠️Special situations▼
Lawn with heavy thatch before overseeding
If your existing lawn has more than half an inch of thatch buildup, dethatch or core aerate before overseeding. Seed needs contact with soil to germinate — thatch acts as a barrier. Rent a core aerator or slit-seeder for best results.
Shady areas with poor grass coverage
Most grass types struggle in deep shade. Fine Fescue is the most shade-tolerant option in cool climates. If an area receives fewer than 4 hours of direct sunlight per day, consider a shade-tolerant ground cover instead of grass.
Large areas over 10,000 square feet
For larger projects, look for bulk seed bags (25–50 lbs) rather than smaller retail bags. The per-pound price drops significantly and you will save substantially on cost. Big-box stores and farm supply stores carry bulk sizes for Tall Fescue and Ryegrass.
Bermuda or Zoysia in cooler climates
Bermuda and Zoysia are warm-season grasses that go dormant and turn brown in fall. They do not thrive north of roughly the Tennessee–Kentucky line. In transition zones, they may survive but look poor for several months of the year.
❓Common questions▼
When is the best time to seed a lawn?
Cool-season grasses (Kentucky Bluegrass, Tall Fescue, Ryegrass, Fine Fescue) should be seeded in late summer to early fall (late August through October in most of the US) when soil temperatures are between 50–65°F. Spring seeding is a second option but competes with weed germination. Warm-season grasses (Bermuda, Zoysia) should be seeded in late spring to early summer when soil temperatures consistently reach 65°F or above.
How long does grass seed take to germinate?
Germination time varies by grass type. Perennial Ryegrass is the fastest at 5–10 days. Tall Fescue germinates in 7–14 days. Kentucky Bluegrass is the slowest at 14–30 days. Bermuda and Zoysia typically take 10–21 days under warm conditions. Keep the seed bed consistently moist — watering lightly two to three times per day — until germination is established.
Do I really need starter fertilizer?
Yes. Starter fertilizer has a higher phosphorus content (the middle number on a fertilizer bag) than regular lawn fertilizer. Phosphorus is critical for root development in newly germinated grass. Using a standard maintenance fertilizer instead can result in slower establishment and patchier coverage, especially in phosphorus-deficient soils.
What is the difference between new seeding and overseeding rates?
New seeding requires higher seed rates because you are relying entirely on the new seed to establish a full stand of grass. Overseeding uses roughly half the rate because existing turf already fills much of the space — you are filling gaps and increasing density, not building from bare soil. Using full new-lawn rates when overseeding wastes seed and can cause excessive competition between seedlings.
Can I use a broadcast spreader for seeding?
Yes — a broadcast (rotary) spreader works well for most grass types. Set the spreader to the rate recommended on your seed bag. For Kentucky Bluegrass and Fine Fescue (which have very small seeds), make two passes at half-rate going in opposite directions for more even coverage. A slit-seeder is a better option for overseeding heavy thatch or compacted soil.