What is window-to-wall ratio?

Window-to-wall ratio is the area of window or glazing openings divided by the relevant gross wall area, expressed as a percentage.

How is window-to-wall ratio calculated?

Divide total window opening area by gross wall area and multiply by 100.

Does WWR use glass area or opening area?

The definition can vary by project or standard, so the calculation should use the area definition specified for the assessment.

Can several windows be included?

Yes. Enter the count of identical windows.

Facade opening analysis

Window-to-Wall Ratio Calculator | Glazing Area %

Calculate the share of a gross wall occupied by window openings. Enter one repeated window or another consistent opening type, then compare total opening area with gross wall area.

Wall and window dimensions

Gross wall width

Gross wall height

Window width

Window height

Window count

Dimension unit

This tool calculates a geometric opening-area ratio. Whether a project calls it WWR, glazing ratio or another metric depends on the applicable project definition and area boundary.

Enter wall and window dimensions.

Window-to-wall ratio

Glazing / opening ratio

—

Total window opening area ÷ gross wall area

—Gross wall area

—Window area

—Opaque remainder

—Window count

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WWR formula

Gross wall area = wall width × wall height
Total window area = window width × window height × number of windows
Window-to-wall ratio = total window area ÷ gross wall area × 100

Why the area definition matters

Some analyses use rough opening area, some use glazing area and some use other defined facade boundaries. This tool reports the exact geometric quantities used so the user can compare them with the project's stated definition.

Why WWR is useful

A window-to-wall ratio provides a simple way to describe how much of a wall is occupied by openings. It can support early facade comparisons, design studies and quantity reviews, but it is not by itself a complete energy, daylight or code analysis.

Worked example

A 12 m × 3 m wall has twelve windows measuring 1.2 m × 1.5 m:

Wall area = 12 × 3 = 36 m²
Window area = 1.2 × 1.5 × 12 = 21.6 m²
Ratio = 21.6 ÷ 36 × 100 = 60%

Frequently Asked Questions

What does a 60% WWR mean?

It means the calculated window-opening area equals 60% of the selected gross wall area.

Does WWR automatically mean glass area?

No. The precise area definition must be identified for the project.

Can I calculate several identical windows?

Yes.

Does this perform an energy analysis?

No. It is an area-ratio calculator.