Egress window size & compliance checker
Screen a bedroom window against the IRC R310 emergency-escape minimums — clear area, width, height and sill height — and see exactly which test passes or fails.
This opening clears 7.50 sq ft and meets the LABELED IRC R310 emergency-escape minimums (5.7 sq ft, ≥ 20 in wide, ≥ 24 in tall, sill ≤ 44 in). Note that meeting the minimum width AND height does not guarantee the clear-opening area — a 20 × 24 in slider is only 3.33 sq ft. This screens against the labeled minimums; final egress compliance is set by your local code and the AHJ — confirm before you order.
Calculator inputs
A sleeping room generally needs an emergency escape and rescue opening — a window a person can climb out of and a firefighter can climb into. The International Residential Code (IRC), Section R310, sets four minimums a window must meet at the same time: a minimum clear opening area, a minimum clear width, a minimum clear height, and a maximum sill height above the floor.
The trap is the clear-opening area. A window can pass the width and height minimums on their own and still fail the area, because the sash, frame and hardware eat into the clear opening. This checker screens all four tests against the labeled IRC R310 values and tells you precisely which one fails.
Formula
clear_area_sqft = clear_width_in × clear_height_in ÷ 144
PASS requires all of:
clear_area ≥ 5.7 sq ft (or ≥ 5.0 for a grade-floor opening) AND clear_width ≥ 20 in AND clear_height ≥ 24 in AND sill_height ≤ 44 in
Worked example
Passes. A casement with a 30 in clear width, 36 in clear height and a 40 in sill, above grade:
area = 30 × 36 ÷ 144 = 7.5 sq ft ≥ 5.7 ✓, width 30 ≥ 20 ✓, height 36 ≥ 24 ✓, sill 40 ≤ 44 ✓ → PASS.
Fails on area. A slider with a 20 in clear width and 24 in clear height meets each dimension on its own (20 ≥ 20, 24 ≥ 24) but:
area = 20 × 24 ÷ 144 = 3.33 sq ft < 5.7 → FAIL on the minimum clear opening area.
What to measure first & how to read the result
- Measure the clear opening, not the frame. Open the window fully and measure the actual unobstructed hole — between the sash and the jamb, not the rough opening or the glass size.
- Window style changes the clear opening. A casement cranks fully open, so nearly the whole unit is clear; a double-hung or slider only opens half, so it needs to be much larger to clear the same area.
- Grade-floor allowance. An opening at or below grade may use the 5.0 sq ft minimum; above-grade openings use 5.7. A window well has its own size and ladder rules.
- This is a screen, not a sign-off. The values here are a labeled IRC R310 snapshot. Your local building code and the authority having jurisdiction (AHJ) set the final requirement — confirm before you order or enlarge an opening.
Reference table
IRC R310 emergency-escape minimums (labeled published snapshot — confirm your local code and AHJ). See the full egress table.
| Requirement | Minimum |
|---|---|
| Min clear opening area (above grade) | 5.7 sq ft |
| Min clear opening area (at/below grade) | 5.0 sq ft |
| Min clear width | 20 in |
| Min clear height | 24 in |
| Max sill height above floor | 44 in |