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Grass Seed Calculator

How Much Grass Seed Do I Need?


Our handy grass seed calculator makes it quick and easy to calculate how much grass seed you’ll need for your garden.

From simple square or rectangular lawns to more intricate designs consisting of circles, triangles, or even octagons, our grass seed calculator will help you determine how much seed you’ll need.

We’ve included a step-by-step user guide below the calculator that will answer any technical queries. You’ll also find several calculation guides showing you how to calculate the quantity of grass seed needed on a per foot, per meter, and per acre basis if you’d prefer to calculate these manually.

Grass Seed Calculator:
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toolcrowd grass seed calculator profile image
Please enter all dimensions above.
Disclaimer: The weights, volumes, and quantities shown in the above calculator are for guidance only and should not form the basis of any calculations where precise or accurate information is required. It isn’t uncommon for theoretical material weights and densities to vary considerably from actual weights and densities, for example, due to differences in manufacturing processes, material compositions, packing densities, and moisture content. Therefore, you should obtain relevant, accurate information from manufacturers or suppliers if exact weight, volume, and quantity calculations are required.

How to Use the Grass Seed Calculator

  1. With our grass seed calculator, you can calculate the amount of grass seed that is required for various area shapes.

    You can choose the relevant profile for your calculation using the ‘Select a Lawn/Area Profile’ dropdown.

    The following profile types are available via the dropdown:

    • Square Area
    • Rectangular Area
    • Circle/Round Area
    • Hexagonal Area
    • Octagonal Area
    • Triangular Area
  2. Use the ‘Application Type’ dropdown in box (2) to choose the type of grass seed application for your calculation, with the following types being available:

    • Overseeding a Lawn
    • Sowing a New Lawn

    You can also choose ‘Custom Application’ if there’s a different grass seed application type that you’d prefer to use.

    The various ‘Density’ boxes will automatically be populated based on the type of application you choose.

    You can update the ‘Density’ figure if needed, although this is based on industry guidance for each asphalt type.

    We would recommend using a custom density value, however, if you have a specific value available from the supplier of the type of grass seed that you’re planning to use.

  3. Depending on the lawn/area shape chosen, you’ll need to enter various dimensions, for example, ‘Length’, ‘Width’, and ‘Diameter’.

    The calculator will automatically reformat depending on the lawn/area shape chosen, meaning only the relevant dimensions will be shown.

    You can select the relevant units (in both metric and imperial) for each measurement using the ‘Unit’ dropdowns.

    !

    Note: If you choose ‘inch’ as a unit, you’ll need to use either whole or decimal numbers instead of fractions. For example, 0.50 instead of 1/2.

  4. Use the ‘Calculate’ button to complete the calculation, and the ‘Reset’ button to reset the grass seed calculator.

How to Calculate How Much Grass Seed You Need

The easiest way to calculate how much grass seed you need is by using the quick and straightforward calculator above.

If you’d prefer to calculate the quantity required manually, though, or you’d like to understand how the calculator works, it all relies on a couple of equations as outlined below.

Step One

First, you’ll need to calculate the size of the area to which you’ll be applying grass seed, and you can do so via one of the following equations for square, rectangular, or round lawns:

Common Grass Seed Calculator Area Formulas

Shape

Area Formula

Terms

Square A = L2 L = length of side
Rectangle A = L x W L = length
W = width
Circle π × r2 π = Pi (3.142)
r = radius

You can find the formulas to calculate the area of other more complex shapes here.

Step Two

The next step is to multiply the lawn area by the density of grass seed required for your application type to find out how much grass seed you’ll need.

For example:

Grass Seed Quantity = Area Size x Grass Seed Density

When it comes to grass seed density, we generally work with the following figures:

Grass Seed Density Guidance

Application Type

Grass Seed Density

Metric

Imperial

Overseeding Existing Grass 25 g/m2 0.0051 lb/ft2
Sowing a New Lawn 35 g/m2 0.0072 lb/ft2

It’s important to note that the above density figures are for guidance only. We recommend using the specific density value quoted by the company supplying your grass seed for the most accurate calculation.

Let’s look at a real-life example calculation to show you step-by-step how to work out how much grass seed you need:

How Much Grass Seed Do I Need for a 100-ft by 50-ft Lawn?

As mentioned above, the first step is to calculate the area of the lawn, which is relatively simple for the rectangular shape in our example, using the following equation:

Lawn Area = Lawn Length x Lawn Width
Lawn Area = 100-ft x 50-ft
Lawn Area = 5,000 ft2

We now have two options depending on whether we’ll be overseeding an existing lawn, or sowing a new one:

Option 1 – Overseeding an Existing Lawn

Based on the table above, we’ll use a grass seed density of 0.0051 lb/ft2 for overseeding as follows:

Grass Seed Quantity = Lawn Area x Grass Seed Density
Grass Seed Quantity = 5,000 ft2 x 0.0051 lb/ft2
Grass Seed Quantity = 25.5 lbs
Option 2 – Sowing a New Lawn

Based on the table above, we’ll use a grass seed density of 0.0072 lb/ft2 for sowing a new lawn as follows:

Grass Seed Quantity = Lawn Area x Grass Seed Density
Grass Seed Quantity = 5,000 ft2 x 0.0072 lb/ft2
Grass Seed Quantity = 36 lbs
Example Summary

A 100-ft by 50-ft lawn would require 25.5 lbs of grass seed for overseeding (based on a density of 0.0051 lb/ft2) or 36 lbs if sown as a new lawn (based on a density of 0.0072 lb/ft2).


Quick Reference Information

How Much Grass Seed Do I Need for Overseeding?

We recommend applying approximately 35 grams of grass seed per square meter for overseeding of existing grass, equivalent to 0.0051 lbs per square foot (or around 5.1 lbs per thousand square feet).

Some grass seeds require a different density, so it’s worthwhile checking the guidance of whichever grass seed you intend to use for best results.

How Much Grass Seed Do I Need for a New Lawn?

We recommend applying approximately 35 grams of grass seed per square meter when sowing new grass, equivalent to 0.0072 lbs per square foot (or around 7.1 lbs per thousand square feet).

Some grass seeds require a different density, so it’s worthwhile checking the guidance of whichever grass seed you intend to use for best results.

How Much Grass Seed Do I Need per Square Foot?

Based on the recommendations above, here’s a summary of the typical grass seed quantity required per square foot:

Grass Seed Quantity per Square Foot

Grass Seed Quantity per Square Foot

Application Type

Typical Quantity of Grass Seed Required

Metric

Imperial

Overseeding Existing Grass 2.32 grams 0.0051 lbs
Sowing a New Lawn 3.25 grams 0.0072 lbs

How Much Grass Seed Do I Need per Square Meter?

Based on the recommendations above, here’s a summary of the typical grass seed quantity required per square meter:

Grass Seed Quantity per Square Meter

Grass Seed Quantity per Square Meter

Application Type

Typical Quantity of Grass Seed Required

Metric

Imperial

Overseeding Existing Grass 25 grams 0.055 lbs
Sowing a New Lawn 35 grams 0.078 lbs

How Much Grass Seed Do I Need per Acre?

Based on the recommendations above, here’s a summary of the typical grass seed quantity required per acre:

Grass Seed Quantity per Acre

Grass Seed Quantity per Acre

Application Type

Typical Quantity of Grass Seed Required

Metric

Imperial

Overseeding Existing Grass 101.17 kg 222.16 lbs
Sowing a New Lawn 141.64 kg 313.63 lbs

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