Egress Window Calculator
Egress opening area and code verdict.
What it does
Egress windows turn bedrooms into exits: fire codes demand openings big enough to climb through with sills low enough to reach. Four numbers decide every window.
The tool above takes clear width, height, sill, and floor. It returns clear area with a pass or fail verdict naming each miss.
The default 24 by 36 with sill 40 upstairs gives 6.0 ft2 and passes all four. The 20 by 20 case gives 2.8 ft2 and fails area with height.
Residential code escape rules set 5.7 upper with 5.0 at grade, 20 inch width minimums, 24 inch height minimums, and 44 inch sill maximums. Builder references repeat the same four gates.
Measure the clear opening, not the frame: sashes, cranks, and center posts eat real inches. Bars and locks must release from inside without keys, tools, or special knowledge.
How to use
- Type clear width.
- Type clear height.
- Type sill height.
- Pick upper or grade floor.
- Read clear area first.
- Read pass or fail beside it.
Formula
- width
- Clear opening width in inches.
- height
- Clear opening height in inches.
- sill
- Sill height above floor in inches.
International Residential Code emergency escape rules fix 5.7 ft2 upper with 5.0 at grade, 20 inch minimum width, 24 inch minimum height, and 44 inch maximum sill. Builder code resources repeat the same four gates for bedroom and basement sleeping rooms. Local amendments can exceed these minimums.
Worked example
Example: upstairs bedroom window
Defaults: 24 x 36, sill 40, upper floor.
- Window: 24 in wide by 36 high, sill 40, upper floor.
- Area: 24 x 36 / 144 = 6.0 ft2.
- Need: 5.7 ft2 for upper floors.
- Widths: 24 clears 20, 36 clears 24, sill 40 clears 44.
- Verdict: passes all four checks.
- Tool shows 6.0 ft2, Passes all four, Needs 5.7 ft2, 20 in wide, 24 in high, sill 44 in max.
Reference table
| Gate | Upper | Grade |
|---|---|---|
| Clear area | 5.7 ft2 | 5.0 ft2 |
| Min width | 20 in | 20 in |
| Min height | 24 in | 24 in |
| Max sill | 44 in | 44 in |
Limits
- Planning check, not permit sign off.
- Clear opening, not frame size.
- Local amendments can exceed.
- Bars need release hardware.
Common mistakes
- Measuring frames not openings.
- Forgetting sill height fails.
- Counting grade rules upstairs.
- Ignoring replacement sash losses.
- Locking bars without releases.
Try it yourself
Quick checks. Answers sit tucked under each question.
20 by 20, sill 40, upper?
2.8 ft2 under 5.7 with height under 24: fails area and height.
24 by 36, sill 48?
6.0 ft2 but sill 48 over 44: fails sill only.
24 by 36, grade floor?
Grade needs 5.0: 6.0 passes with room to spare.
Questions
IRC numbers?
5.7 ft2 upper floors, 5.0 at grade, with 20 in minimum width, 24 in minimum height, and 44 in maximum sill.
Which rooms?
Bedrooms and basements with sleeping rooms need them. Living rooms generally do not.
Three of four enough?
No, all four gates pass together: area, width, height, and sill.
Basement wells?
Ladders, steps, and window wells serve below grade openings with covers that open freely.
Replacement windows?
Yes, replacement sashes must hold the same clear opening. Check labels before ordering.
Security bars?
Locks, bars, and grilles must release from inside without keys or tools.