Grass Seed Calculator
Estimate how much grass seed to buy from lawn size, grass type, and project type, then review typical seeding rate, bag counts, and optional budget for a new lawn or overseeding job.
Grass Seed Inputs
Tall Fescue | New lawn
Seed Quantity Summary
Seed required
12 lb
5.44 kg total from 2,000 sq ft at 6 lb / 1,000 sq ft.
Coverage area
2,000 sq ft
185.8 sq m
Typical rate
6 lb / 1,000 sq ft
New lawn
Germination
6-12 days
Cool-season / transition-zone
Seed-only cost
$48.00
At $4.00 per lb
Current Calculation
Area = length x width
50 ft x 40 ft = 2,000 sq ft
Seed required = area (sq ft) / 1,000 x seeding rate
2,000 / 1,000 x 6 = 12 lb
Bag count = round up(seed required / bag size)
5 lb: 3 | 10 lb: 2 | 25 lb: 1 | 50 lb: 1
Estimated cost = seed required x price per lb
12 x $4.00 = $48.00
Grass Type Notes
- Bare-soil seeding needs full coverage, so the calculator uses the species-specific new-lawn rate.
Use Scenarios
Pricing a bare-soil lawn project
Use the page before you buy seed for a new lawn, renovation, or full tear-out so you can translate length and width into a realistic seed weight instead of guessing from bag marketing.
Planning a lighter overseeding pass
If the lawn still has live turf but looks thin, the calculator applies a lighter planning rate so you can compare a repair pass with a full bare-soil seeding job.
Comparing grass types before checkout
Switch between cool-season and warm-season species to see how the typical rate, germination window, and bag count change before you commit to one seed type or mix.
Formula Explanation
1) Measure the lawn area
Area = length x width
The calculator assumes a rectangular footprint. If the lawn is irregular, break it into smaller rectangles, calculate each section, and add the total area before you buy seed.
2) Choose the project rate
Rate = species default for new lawn or overseeding
Each grass type uses a typical planning rate. New-lawn mode applies the full bare-soil rate, while overseeding mode uses a lighter pass for existing turf.
3) Convert area into seed weight
Seed required = area (sq ft) / 1,000 x seeding rate
This gives the exact seed weight in pounds, then the page converts that weight into kilograms so imperial and metric planning stay aligned.
4) Round to purchasable bags
Bag count = round up(seed required / bag size)
Bag math is shown for 5 lb, 10 lb, 25 lb, and 50 lb sizes. The optional price field estimates seed-only spend at the entered per-pound cost before tax or delivery.
How to Read the Result
Exact weight vs. bag count
The main result is the exact seed weight from the formula. Bag counts are rounded up to real package sizes, so the purchased amount will usually be a little higher than the exact weight.
Project type changes the weight
The same lawn can return very different seed weights when you switch between new-lawn and overseeding modes because one assumes bare soil and the other assumes existing turf still covers part of the surface.
Grass-type notes matter
Climate fit, germination speed, and establishment method can matter as much as the bag count. St. Augustinegrass is the clearest example because it is usually planted vegetatively instead of from seed.
Example Cases
Case 1: 50 x 40 ft tall-fescue lawn
Inputs
- Lawn size: 50 x 40 ft
- Grass type: Tall Fescue
- Project type: New lawn
- Price: $4.00 per lb
Computed Results
- Area: 2,000 sq ft
- Rate: 6 lb / 1,000 sq ft
- Seed: 12 lb / 5.44 kg
- Bag read: 2 x 10 lb or 1 x 25 lb
- Cost: $48.00
Interpretation
This is a straightforward bare-soil project with a common transition-zone grass. The exact seed requirement is high enough that the purchase decision quickly becomes a bag-size question rather than a rate question.
Decision Hint
Use a case like this to compare one 25 lb bag against a stack of smaller bags and to decide whether a full renovation still fits the project budget.
Case 2: 60 x 30 ft perennial-rye overseeding
Inputs
- Lawn size: 60 x 30 ft
- Grass type: Perennial Ryegrass
- Project type: Overseeding
- Price: $3.50 per lb
Computed Results
- Area: 1,800 sq ft
- Rate: 3 lb / 1,000 sq ft
- Seed: 5.4 lb / 2.45 kg
- Bag read: 1 x 10 lb or 1 x 25 lb
- Cost: $18.90
Interpretation
The overseeding setting lowers the planning rate because live turf still exists. That keeps the bag count more realistic for a density repair instead of a full restart.
Decision Hint
If the lawn is thinner than expected once you rake or dethatch, rerun the same area in new-lawn mode and compare the material jump before you buy seed.
Case 3: 18 x 12 m bermuda project
Inputs
- Lawn size: 18 x 12 m
- Grass type: Bermuda Grass
- Project type: New lawn
- Price: $7.00 per lb
Computed Results
- Area: 216 sq m
- Rate: 1 lb / 1,000 sq ft
- Seed: 2.33 lb / 1.05 kg
- Bag read: 1 x 10 lb or 1 x 25 lb
- Cost: $16.28
Interpretation
This metric example shows how a large warm-season lawn can still need a modest seed weight because the species rate is much lighter than a cool-season fescue or ryegrass project.
Decision Hint
Keep the metric area for local planning, but compare bag sizes and warm-weather timing before you lock in a seeding date.
Boundary Conditions
Sources & References
- Cornell University Safe Sports Fields - Seeding RatesUsed for the core seeding-rate framework and the reminder that pure-live-seed percentage changes how much material must be purchased.
- University of Tennessee Extension - Selecting Grass SeedUsed for species-specific lawn-seeding ranges and warm-season germination notes across common turf types such as bermudagrass, zoysia, and centipedegrass.
- University of Maryland Extension - Lawn Renovation and OverseedingUsed for cool-season renovation timing, overseeding workflow, and the reminder that thin lawns need seed-to-soil contact rather than a heavy blind spread over thatch.
- Cornell Turfgrass Program - Choose SeedUsed for species and seed-mix guidance, especially why the actual bag label matters when blends and varieties change the real coverage pattern.
- UF/IFAS Extension - St. Augustinegrass for Florida LawnsUsed for the boundary note that St. Augustinegrass is normally established vegetatively rather than from seed and should be planted during active growth.