Home & Construction
Window Size Calculator - Calculate optimal window size for natural lighting
Calculate optimal window size for natural lighting
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
What is the minimum window requirement?
Building codes typically require windows equal to 10-12% of floor area for habitable rooms.
Do bathrooms need windows?
Not required if mechanical ventilation exists, but recommended for natural light and ventilation.
What about egress windows?
Bedrooms require egress windows (min 5.7 sq ft opening) for emergency escape.
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About this tool
This Window Size Calculator turns your inputs into practical results. Provide Room Floor Area, Room Type, and Lighting Preference to calculate Minimum Window Area and Recommended Window Area.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.