Egress clear opening calculator
A window that fails egress fails it after it is installed, which is the expensive moment to find out. Put the unit size in below and see what a person actually gets through.
What this does and does not do. It applies the code arithmetic to the dimensions you type. It cannot know the real net clear opening of your unit, because that depends on the frame and sash profile and is printed on the manufacturer’s cut sheet. Where the two disagree, the cut sheet and your building department win. Use this to catch a problem before you order, not to certify a window.
The four numbers that all have to pass
Under the 2025 California Residential Code, section R310.2.1, an emergency escape and rescue opening has to satisfy every one of these at the same time. Meeting three of four is a fail.
- Net clear opening of at least 5.7 square feet — or 5.0 at grade floor level
- Net clear opening height of at least 24 inches
- Net clear opening width of at least 20 inches
- Bottom of the clear opening no more than 44 inches above the finished floor
It also has to be openable from the inside without a key, a tool, or special knowledge. Security bars are allowed only if they release the same way.
Minimum clear height for a given clear width
Plenty of square footage and still a fail is normal — a wide, short opening clears the area and misses the height. This is the shortest a clear opening can be at a given clear width.
| Clear width | Min clear height — 5.7 sq ft | Min clear height — 5.0 sq ft (grade) |
|---|---|---|
| 20″ | 41.04″ | 36″ |
| 21″ | 39.09″ | 34.29″ |
| 22″ | 37.31″ | 32.73″ |
| 23″ | 35.69″ | 31.3″ |
| 24″ | 34.2″ | 30″ |
| 25″ | 32.83″ | 28.8″ |
| 26″ | 31.57″ | 27.69″ |
| 27″ | 30.4″ | 26.67″ |
| 28″ | 29.31″ | 25.71″ |
| 29″ | 28.3″ | 24.83″ |
| 30″ | 27.36″ | 24″ |
| 31″ | 26.48″ | 24″ |
| 32″ | 25.65″ | 24″ |
| 33″ | 24.87″ | 24″ |
| 34″ | 24.14″ | 24″ |
| 35″ | 24″ | 24″ |
| 36″ | 24″ | 24″ |
Why unit size is not clear opening
This is the distinction that costs people money, and it is the reason this calculator exists.
- A horizontal slider gives up roughly half its width to the fixed panel and the meeting rail. A 58½ inch unit leaves about a 29¼ inch clear width.
- A single or double hung unit keeps its full width but gives up half its height, because only one sash passes the other.
- A casement or awning opens close to the full frame, which is why they so often succeed where a slider fails in the same opening.
- A fixed or picture window has no clear opening at all. It cannot be an egress window, whatever its size.
Two windows with the same call-out dimension can have very different clear openings, because the frame and sash profile eat into it differently. That is why a like-for-like replacement can turn a compliant bedroom into a failed inspection.
Questions contractors ask
What is the minimum size for a bedroom egress window in California?
Four measurements, and all four have to pass at once: at least 5.7 square feet of net clear opening, at least 24 inches of clear height, at least 20 inches of clear width, and the bottom of the clear opening no more than 44 inches above the floor. Grade-floor openings are allowed 5.0 square feet instead of 5.7. That is the 2025 California Residential Code, section R310.2.1.
What is the difference between net clear opening and window size?
The unit size is what you order. The net clear opening is the hole a person actually gets through once the sash is open, measured at the narrowest point. They are not the same number, and the gap between them is where most egress failures come from. Inspectors measure the clear opening, not the frame or the glass.
How is clear opening worked out on a slider?
A horizontal slider gives up half its width to the fixed panel and the meeting rail. A 58 1/2 inch unit leaves roughly a 29 1/4 inch clear width. Its height is essentially the full frame height.
And on a single or double hung window?
The opposite: a hung unit keeps its full width but gives up half its height, because only one sash opens past the other.
What is the maximum sill height?
The bottom of the clear opening cannot be more than 44 inches above the finished floor. Note the word finished. Carpet, tile and a raised platform all count, and inspecting against the subfloor is how people end up failing a final.
When is 5.0 square feet allowed instead of 5.7?
At grade floor level, so a window you can step straight out of. A second-floor or basement opening needs the full 5.7 square feet.
Does a fixed window count as egress?
No. It has to be openable from the inside without a key, a tool, or special knowledge. Security bars are allowed only if they release from the inside the same way.
How accurate is this calculator?
It does the code arithmetic on the dimensions you enter. What it cannot know is the real net clear opening of your specific unit, which depends on the frame and sash profile and is printed on the manufacturer's cut sheet. Where the two disagree, the cut sheet and your building department win. Use this to catch a problem before you order, not to certify a window.
Does this apply to basement windows?
Yes, with more attached. A below-grade opening usually also needs a compliant window well sized so the sash can open fully, and a deep well may need a ladder or steps. This calculator does not check the well.
Related: how we get your draws out, what California paperwork actually requires, and the difference between an assistant and a project manager.
Somebody should be checking this before the order goes out
Every measurement on our jobs is checked against the code before it becomes a purchase order. It is arithmetic, not opinion — and it is the part of the job a general assistant cannot do.
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