Grass Seed Rate Calculator
*Recommendation includes a small buffer for uneven spreading.
Grass Seed Rate Calculator: Calculate the Perfect Amount
Whether you are establishing a lush new lawn from bare soil or overseeding an existing turf to thicken it up, knowing exactly how much grass seed to buy is crucial. Applying too little seed results in a thin, patchy lawn that is susceptible to weeds, while applying too much causes competition between seedlings, leading to rot and widespread failure.
This Grass Seed Rate Calculator helps homeowners and landscape professionals determine the precise weight of seed required based on area size, grass species, and the type of planting project.
How to Calculate Grass Seed Needs
To calculate the amount of grass seed required manually, you need three pieces of data:
- Lawn Area: The total size of the project in square feet.
- Seeding Rate: The recommended pounds of seed per 1,000 square feet for your specific grass type.
- Project Type: Whether you are planting a new lawn or overseeding.
The general formula used by turf specialists is:
(Total Square Footage / 1,000) × Recommended Rate = Total Pounds Needed
Recommended Seeding Rates by Grass Type
Different grass species have vastly different seed sizes. For example, Kentucky Bluegrass seeds are tiny (over 1 million seeds per pound), so you need fewer pounds to cover an area compared to Tall Fescue, which has much larger seeds (approx. 220,000 seeds per pound).
- Tall Fescue: 6 to 10 lbs per 1,000 sq. ft.
- Perennial Ryegrass: 7 to 9 lbs per 1,000 sq. ft.
- Fine Fescue: 3 to 6 lbs per 1,000 sq. ft.
- Kentucky Bluegrass: 2 to 3 lbs per 1,000 sq. ft.
- Bermudagrass (Hulled): 1.5 to 2.5 lbs per 1,000 sq. ft.
- Zoysia: 1 to 3 lbs per 1,000 sq. ft.
- Bahia: 5 to 10 lbs per 1,000 sq. ft.
- Centipede: 0.25 to 0.5 lbs per 1,000 sq. ft.
New Lawn vs. Overseeding Rates
The amount of seed you use depends heavily on the state of the soil you are planting into.
New Lawns (Bare Soil)
When planting on bare dirt, you use the full recommended rate. You are trying to establish a complete canopy from scratch. If you calculate too low here, weeds will take over the empty spaces before the grass matures.
Overseeding (Existing Lawns)
When you are overseeding to thicken a thin lawn, you generally use 50% (half) of the new lawn rate. Since there is already established grass, the new seeds need less density to fill in the gaps. Applying the full rate during overseeding can choke out the existing grass.
How to Measure Your Lawn Area
Accurate measurement is the foundation of a successful seeding project. If your lawn is a simple rectangle, multiply the length by the width (Length × Width = Area).
For complex shapes, break the lawn into smaller rectangles or triangles, calculate the area of each, and add them together. If you measured in acres, remember that 1 Acre = 43,560 Square Feet.
Tips for Successful Seeding
- Soil Contact: Seed must touch soil to grow. Rake the area before spreading seed.
- Starter Fertilizer: Use a fertilizer high in phosphorus to encourage root growth.
- Watering: Keep the soil consistently moist (but not soggy) until the seeds germinate. This often means watering lightly 2-3 times a day.
- Spreader Settings: Check your seed bag for the recommended spreader setting. It is better to do two passes at a half-rate (in a crisscross pattern) than one pass at a full rate to ensure even coverage.