Egress Window Size Requirements
The referenced IRC criteria evaluate net clear opening area, minimum opening width, minimum opening height and the height of the bottom of the clear opening above the room floor.
Clear Opening Is Not Window Size
The relevant measurement is the space actually available when the window is normally opened. Frame size, rough opening and nominal product dimensions can therefore be misleading.
Why 20 × 24 Inches Is Not Enough
The minimum width and minimum height are independent requirements. A 20-inch by 24-inch clear opening is only about 3.33 square feet, so it does not meet the separate 5.7-square-foot area criterion.
Frequently Asked Questions
What is the minimum egress window opening area?
The IRC reference threshold is generally 5.7 square feet of net clear opening, with a 5.0-square-foot exception for qualifying grade-floor emergency escape and rescue openings.
What is the minimum egress window width?
The referenced IRC minimum net clear opening width is 20 inches.
What is the minimum egress window height?
The referenced IRC minimum net clear opening height is 24 inches.
What is the maximum egress window sill height?
The bottom of the clear opening is generally limited to 44 inches above the floor under the referenced IRC criteria.
Does passing this calculator make a basement room a legal bedroom?
No. The tool checks selected emergency escape and rescue opening dimensions only. Local bedroom, permitting, smoke-alarm and other building-code requirements can also apply.