Egress Window Calculator
Enter your window opening dimensions to instantly check whether it meets the IRC R310 net-clear-opening requirements for a legal bedroom or basement egress window.
With a 30 in opening height, you need at least 27.4 in of width to reach the 5.7 sq ft area minimum.
With a 30 in opening width, you need at least 27.4 in of height to reach the 5.7 sq ft area minimum.
Based on the IRC R310 (International Residential Code). Local amendments vary — confirm the adopted edition and requirements with your building official before ordering or installing a window.
Understanding Egress Window Requirements
Every sleeping room and most basements must have an emergency escape and rescue opening. Under IRC R310, that opening needs a net clear opening area of at least 5.7 square feet(5.0 square feet for grade-floor openings), a minimum opening height of 24 inches, a minimum opening width of 20 inches, and a sill no more than 44 inches above the floor.
The key trap is that meeting the 24-inch and 20-inch minimums at the same time only yields 3.33 square feet — far short of 5.7. The net clear opening is measured when the window is fully open, so hardware and the sash can reduce it. Use the helper above to see the minimum complementary dimension your opening needs to clear the area requirement.
Frequently Asked Questions
What is the minimum egress window size?
Under IRC R310 the net clear opening must be at least 5.7 square feet (5.0 for grade-floor openings), with a minimum opening height of 24 inches, a minimum opening width of 20 inches, and a sill no higher than 44 inches above the floor.
Can a 20x24 window meet egress?
No. A 20-inch by 24-inch opening is only 3.33 square feet (20 × 24 ÷ 144), which is well below the 5.7 square feet required. The width and height minimums must be met while still reaching the area minimum.
What is the maximum sill height for an egress window?
The bottom of the clear opening can be no more than 44 inches above the finished floor, so an occupant can reach and climb out in an emergency. Window wells are required when the sill falls below grade.
Turn Your Measurements Into a Real Floor Plan
Once you know your dimensions, generate a labeled, to-scale floor plan in seconds — then export it to DXF or build it in 3D. No CAD experience needed.
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