🔢 Free Tool
Egress Window Compliance Calculator
Check if your window meets IRC Section R310 egress requirements for basement and sleeping room windows. Enter your measurements below — results are instant.
Enter Your Window Measurements
All measurements in inches. Measure the open window at its narrowest point.
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WORKPRO Combination Square — Measure Your Egress Opening Accurately
After using the calculator above, you will need to physically measure your window opening. The WORKPRO combination square set (Amazon's Choice, 4.8 stars, 3,997 reviews) includes a 7-inch rafter square and 12-inch combination square — the two tools that handle every IRC R310 measurement: net clear height, width, and sill height from floor.
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IRC R310 Requirements Reference
| Requirement | Basement/Above Grade | Grade Floor (Exterior at Grade) |
|---|---|---|
| Net clear opening area | 5.7 sq ft minimum | 20.4 sq ft minimum |
| Net clear opening height | 24 inches minimum | 24 inches minimum |
| Net clear opening width | 20 inches minimum | 20 inches minimum |
| Sill height from finished floor | 44 inches maximum | 44 inches maximum |
Source: International Residential Code (IRC) Section R310. All 50 states have adopted the IRC in some form; local amendments may vary.
Estimated Frame Deductions by Window Type
These are typical deductions from rough opening to net clear opening. Actual deductions vary by manufacturer — always measure with the window installed and fully open.
| Window Type | Width Deduction | Height Deduction | Opening Fraction |
|---|---|---|---|
| Casement (full crank-out) | ~2.5–3.5" | ~2.5–3.5" | ~90–95% of sash area |
| Double-hung (bottom sash) | ~3–4" | ~4–5" per sash | ~45–50% of window area |
| Single-hung | ~3–4" | ~4–5" | ~45–50% of window area |
| Horizontal slider (half) | ~3–4" per half | ~3–4" | ~45–50% of window area |
| Awning | ~2.5–3.5" | ~2.5–3.5" | ~85–90% of sash area |
Next Steps
Full Egress Guide
Everything about egress requirements, permits, window wells, and inspection.
→Basement Egress Permit
Step-by-step permit process for adding or enlarging a basement egress window.
→How to Measure
Detailed guide to measuring net clear opening correctly, with diagrams.
→Permit Checklist
Free printable checklist for your egress window permit application.
→