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Egress window calculator: is my window big enough for egress?

Passes: 5.81 sq ft

clear opening; needs 5.7 sq ft, 24 in high, 20 in wide, sill 44 in max · well 9 sq ft, 36 in each way · for a 22 × 38 in basement window

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Enter it the way you measured it: 4.5, 4 1/2, 3/8 or 10' 6".

Passes: 5.81 sq ft

clear opening; needs 5.7 sq ft, 24 in high, 20 in wide, sill 44 in max · well 9 sq ft, 36 in each way

    Source: 2021 International Residential Code, R310 Emergency Escape and Rescue Openings (2021 Seattle Residential Code, chapter 3, no Washington amendment to R310.2.1-R310.2.3 or R310.4), read October 24, 2026. Data sheet (PDF)

    A 22 × 38 inch net clear opening gives 5.81 sq ft, enough for a basement egress window: IRC 2021 R310 asks for 5.7 sq ft, 24 in high and 20 in wide at least, with the sill 44 in or less above the floor.

    A worked example

    A second floor casement opening 19 1/2 in wide and 44 in high, with the sill 36 in above the floor needs Fails: 5.96 sq ft. 5.96 sq ft clears the 5.7 sq ft minimum, but the opening is 1/2 in narrower than the 20 in minimum of R310.2.2, so the window does not qualify. The clear sizes are the ones you get with the window opened the normal way, not the frame or the rough opening.

    What size does an egress window have to be?

    A net clear opening of at least 5.7 sq ft (5 sq ft on a grade floor), at least 24 in high and 20 in wide, with the bottom of the opening 44 in or less above the floor: IRC 2021 R310.2. At the 20 in minimum width the opening has to be 41 1/8 in high to reach 5.7 sq ft; at the 24 in minimum height, 34 1/4 in wide.

    How big does an egress window well have to be?

    At least 9 sq ft, reaching at least 36 in out from the wall and 36 in wide (IRC 2021 R310.4.1), and large enough for the window to open fully. Deeper than 44 in, it needs a permanently fixed ladder or steps (R310.4.2), with rungs at least 12 in wide and no more than 18 in apart.

    What else it is called

    The IRC calls it an emergency escape and rescue opening; it is the basement bedroom window, escape window or egress window, and the area well is the window well. Searched as an egress window calculator, egress window size calculator or basement egress window calculator.

    Minimum clear height by clear width

    Minimum net clear height of an egress window for each net clear width
    Clear widthClear height for 5.7 sq ftClear height for 5 sq ft (grade floor)
    20 in 41 1/8 in36 in
    22 in 37 3/8 in32 3/4 in
    24 in 34 1/4 in30 in
    26 in 31 5/8 in27 3/4 in
    28 in 29 3/8 in25 3/4 in
    30 in 27 3/8 in24 in
    32 in 25 3/4 in24 in
    36 in 24 in24 in

    Minimum net clear height for each net clear width, rounded up to the 1/8 in, never under 24 in: IRC 2021 R310.2.1 and R310.2.2. The sill of the clear opening also has to sit 44 in or less above the floor (R310.2.3).

    Where the numbers come from

    Measure the opening with the window opened the normal way: a casement, a slider and a double-hung of the same frame size open to very different clear sizes, and the frame size on the label is not the clear opening.

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