Egress Window Calculator

Calculate egress window requirements for basement bedrooms. Verify minimum opening dimensions, net clear area, sill height, and well size to meet IRC code requirements for emergency exit.

🏗️ Code Compliance🏗️ Net Clear Area = Open Width x Open Height >= 5.7 sq ft

Window opening width (inches)

Window opening height (inches)

Sill height above floor (inches)

Window well diameter or width (in)

Please enter valid values.

Formula & Reference

Variable	Formula	Units
Egress Window Calculator	Net Clear Area = Open Width x Open Height >= 5.7 sq ft	sq ft net clear

Step-by-Step Examples

Example 1

Standard Egress Window

20-in wide, 24-in high, 36-in sill, 36-in well.

Net area = (20/12) x (24/12) = 1.67 x 2.0 = 3.33 sq ft
FAIL - net area 3.33 < 5.7 sq ft minimum
Need larger window: try 20x44 = 6.11 sq ft PASS

✓ FAIL - not large enough for egress (3.33 sq ft < 5.7 min)

Example 2

Passing Egress Window

36-in wide, 24-in high, 36-in sill, 36-in well.

Net area = (36/12) x (24/12) = 3.0 x 2.0 = 6.0 sq ft
PASS - 6.0 > 5.7 sq ft
Width 36 PASS | Height 24 PASS | Sill 36 PASS

✓ PASS - meets all IRC egress requirements

Example 3

Large Egress Window

44-in wide, 24-in high, 44-in sill, 48-in well.

Net area = (44/12) x (24/12) = 8.8 sq ft
PASS on area, width, height
Sill 44in = max allowed under IRC
Well 48in > 36in minimum = PASS

✓ PASS - all requirements met

Real-World Applications

🏗️

Contractors

Verify egress compliance before finishing a basement bedroom.

🏠

Homeowners

Check if your current window meets code before adding a basement bedroom.

⚖️

Building Inspectors

Quickly verify window dimensions against IRC egress requirements.

💰

Real Estate

Basement bedrooms increase home value only if they have proper egress.

Common Mistakes to Avoid

⚠️

Measuring rough opening instead of clear opening

The required 5.7 sq ft is the NET CLEAR opening of the open window, not the rough opening or overall window size. Measure the actual open area with the window in its maximum open position.

⚠️

Forgetting that double-hung windows may not fully open

Some double-hung windows only open the bottom half. The net clear opening on a 3x4 window may be only 1.5x4 = 6 sq ft - which may pass - but verify with the window spec sheet.

⚠️

Building a bedroom without egress

Any room used as a sleeping room legally requires egress. An un-egress-compliant basement room cannot be legally listed or sold as a bedroom, even if it has a closet.

Frequently Asked Questions

What are IRC egress window requirements? ▾

IRC Section R310: Net clear opening of at least 5.7 sq ft (ground floor: 5.0 sq ft). Minimum clear opening height: 24 inches. Minimum clear opening width: 20 inches. Maximum sill height: 44 inches.

How big is a 5.7 sq ft egress window? ▾

Many combinations work: 20-in wide x 41.6-in high = 5.78 sq ft. 24-in x 28.5-in = 5.7 sq ft. 36-in x 24-in = 6.0 sq ft. A 30x27-inch net opening barely meets requirements.

What size window well for egress? ▾

If window well is more than 44 inches deep, it must be at least 36 inches wide and provide a permanent step or ladder. Well must drain properly to prevent flooding.

Can I add egress to an existing basement? ▾

Yes. Egress window installation typically costs $2,500-5,000 per window including cutting the foundation wall, waterproofing, window well, and drain. Requires a building permit in most jurisdictions.

Does every basement window need to be egress? ▾

No - only windows in sleeping rooms (bedrooms). Living rooms, bathrooms, and utility rooms do not require egress windows. A basement family room doesn't need egress; a basement bedroom does.