Glass g Value Calculator



Calculating the g-value, also known as the solar heat gain coefficient (SHGC), is crucial for assessing a window’s energy efficiency. This metric indicates how much solar energy is admitted through a glass product, influencing heating and cooling needs in buildings. This article introduces a simple yet accurate way to compute the g-value using a straightforward formula, accompanied by a user-friendly online calculator.

How to Use

To use the glass g value calculator, enter the necessary parameters into the designated input fields on the calculator form. These parameters generally include the glass type, thickness, and coatings, among other specific characteristics that influence solar gain. Once the required data is input, click the “Calculate” button to view the result.


The formula used for calculating the g-value involves the ratio of solar energy transmitted to the total solar energy incident on the glass. It is expressed as:

This calculation considers both direct transmittance and absorbed energy later re-radiated inward.

Example Solve

For instance, if a glass pane allows 500 Watts of solar energy to pass through when 1000 Watts of solar energy is incident on it, the g-value calculation would be:

This means 50% of the incident solar energy is admitted through the glass.


What does a higher g-value indicate?

A higher g-value indicates that more solar heat is transmitted through the glass, which can be beneficial in colder climates but problematic in warmer ones.

How does glass thickness affect the g-value?

Generally, thicker glass can lead to a lower g-value, as it absorbs more heat than thinner glass.

Can the g-value vary with different types of coatings?

Yes, coatings designed to reflect or absorb solar energy can significantly alter the g-value of glass.


Understanding and calculating the g-value of glass can greatly aid in making informed decisions about glass products for energy efficiency in buildings. The provided calculator simplifies this process, allowing for quick and accurate assessments tailored to specific needs.

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