What are the egress window requirements for a basement?

In the IRC: net clear opening of 5.7 sq ft (5 sq ft below grade in the edition we checked), 24 in high, 20 in wide, sill no higher than 44 in, and a window well of at least 9 sq ft with 36 in projection.

Does a window well need a ladder?

When it is deeper than 44 in, the IRC requires a permanently fixed ladder or steps usable with the window fully open.

Does a bedroom in a basement need an egress window?

The IRC requires an emergency escape opening in basements and every sleeping room, with listed exceptions. Your local code governs.

Is cutting an egress opening a structural job?

Cutting a foundation wall changes how it carries load. Get a permit and, where the building department asks, an engineer’s detail for the header.

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Egress window size requirements checker

Clear opening area, height, width, sill and window well, checked against the model-code minimums.

Egress window size requirements in the IRC are a net clear opening of at least 5.7 sq ft, at least 24 inches high and 20 inches wide, with a sill no more than 44 inches above the floor.

In the edition we checked, grade-floor and below-grade openings may be 5 sq ft. A window well must be at least 9 sq ft with 36 inches of projection and width, and a ladder is needed past 44 inches deep.

Egress window requirements checker

Clear opening area, height, width, sill and window well, checked against the model-code minimums.

— Result

— Clear opening

— Checks

— Window well

What this assumed —

Model-code minimums. Your local edition and amendments govern.

The IRC R310 minimums

Item	Minimum	Section
Net clear opening	5.7 sq ft (5 sq ft grade-floor or below-grade in the edition checked)	R310.2.1
Clear height	24 in	R310.2.1
Clear width	20 in	R310.2.1
Sill height	No more than 44 in above the floor	R310.2.2
Window well	9 sq ft, 36 in projection and width	R310.2.3
Ladder or steps	Required when the well is deeper than 44 in	R310.2.3.1

Measuring it right

Measure the opening, not the frame. The code means the clear space you could climb through in normal operation. A 24 × 36 in clear casement gives 6 sq ft; a double-hung sash rarely reaches 5.7.

Editions differ. Section numbers and the below-grade allowance changed between IRC editions. Ask your building department which one it enforces before you cut a foundation wall, and see foundation types for what you are cutting into.

Questions this calculator answers

What are the egress window requirements for a basement?: In the IRC: net clear opening of 5.7 sq ft (5 sq ft below grade in the edition we checked), 24 in high, 20 in wide, sill no higher than 44 in, and a window well of at least 9 sq ft with 36 in projection.
Does a window well need a ladder?: When it is deeper than 44 in, the IRC requires a permanently fixed ladder or steps usable with the window fully open.
Does a bedroom in a basement need an egress window?: The IRC requires an emergency escape opening in basements and every sleeping room, with listed exceptions. Your local code governs.
Is cutting an egress opening a structural job?: Cutting a foundation wall changes how it carries load. Get a permit and, where the building department asks, an engineer’s detail for the header.

Sources and methodology

Figures dated 26 October 2026. Last reviewed August 16, 2026.

Emergency escape and rescue openings fact sheet: IRC R310.2.1 area, height and width, R310.2.2 sill, R310.2.3 window wells and R310.2.3.1 ladders (Minnesota Department of Labor and Industry, retrieved 2026-10-26. Minnesota’s adopted IRC text. Other states adopt other editions.)

Foundation types What you are cutting into.
Basement waterproofing Wells need drainage.
Do I need a structural engineer When a cut needs a design.

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Egress window requirements checker

The IRC R310 minimums

Measuring it right

Questions this calculator answers

Sources and methodology

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