Free Grass Seed Calculator

Grass Seed Calculator — Determine Your Exact Seed Quantity

Whether you are establishing a brand‑new lawn or overseeding an existing one, knowing exactly how much grass seed you need avoids waste and ensures even coverage. This free online lawn seeding calculator takes the guesswork out of the process: you input the dimensions of your turf and the seed’s coverage rate, and it instantly returns the required weight of seed in pounds or kilograms. No matter whether you prefer a grass seed coverage calculator that works in imperial or metric units, this tool has you covered.

Step‑by‑Step Use

1. Choose the shape of your lawn — the calculator supports rectangular, circular, elliptical, and triangular plots. For each shape you only need two or three linear measurements (width and length for rectangles; radius for circles; axis A and axis B for ellipses; base and height for triangles).
2. Enter the dimensions in your preferred unit (feet or meters). The tool handles unit conversion automatically, so you never have to worry about mixing feet and inches.
3. Provide the seed’s coverage rate (also called the seeding density). This value is almost always printed on the seed bag and differs depending on whether you are creating a new lawn or overseeding an existing one. If you are unsure, refer to the typical rates listed below or ask your local garden center.

After these three steps, the calculator displays the total seed weight required for the entire area.

Area Formulas Used

The tool computes the lawn area with standard geometric formulas:

• Rectangle: $\text{Area} = \text{width} \times \text{length}$
• Circle: $\text{Area} = \pi \times \text{radius}^{2}$
• Ellipse: $\text{Area} = \pi \times \text{axis}_{A} \times \text{axis}_{B}$
• Triangle: $\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}$

All results are expressed in square feet (or square meters) before the seed weight calculation.

Seed Weight Calculation

Once the area is known, the required seed weight is found with this formula:

$$\text{Seed weight (lbs)} = \frac{\text{coverage rate (lbs per 1000 sq ft)} \times \text{area (sq ft)}}{1000}$$

For example, imagine a circular lawn with a radius of 50 ft. Its area is

$$\pi \times 50^{2} \approx 7\,854\ \text{sq ft}$$

If you choose a grass with a coverage rate of 5 lbs per 1,000 sq ft (typical for fine fescue on a new lawn), the calculator gives:

$$\frac{5 \times 7\,854}{1000} \approx 39.27\ \text{lbs}$$

This same relationship works for any shape and any seed type — simply multiply the area by the rate and divide by 1,000. The tool also supports metric rates (kg per 100 m²) and automatically converts between units.

Understanding Coverage Rates

The coverage rate (seeding density) varies among grass species and depends on whether you are sowing a new lawn or overseeding. Rates are usually listed on the seed package, but the table below provides representative values for common cool‑season grasses. These values show how much grass seed per square foot is typically recommended.

Grass Type	New Lawn (lbs / 1000 ft²)	Overseeding (lbs / 1000 ft²)
Buffalo	3	1.5
Creeping Red Fescue	5	2.5
Fine Fescue	5	2.5
Kentucky Blue Grass	4	2
Tall Fescue	10	5

For overseeding, the rate is typically half the new‑lawn rate. Always check the product label for the manufacturer’s exact recommendation, as using too much seed can lead to overcrowding and poor lawn health, while too little may result in bare patches.