🆓 Free construction tool
Window & Door Rough Opening Calculator
Decode nominal window sizes, size door rough openings, and build a quick skylight opening summary with a simple shaft-angle check.
Nominal size
0
Rough opening width
0
Rough opening height
0
Header recommendation
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Trimmer studs
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Door header quick table
| Span | Recommended header |
|---|---|
| Up to 4 ft | 4×6 |
| 4–6 ft | 4×8 |
| 6–8 ft | 4×10 |
| 8–10 ft | 4×12 |
| 10–12 ft | Doubled 2×12 + LVL |
Framing reminders
- Verify manufacturer rough opening tolerances before framing custom windows or exterior doors.
- Header sizing depends on load path, wall type, and local code — use this as a quick field guide only.
- Skylight shafts often flare toward the room to increase daylight spread.
Frequently Asked Questions
How do I read a window size like 3060?
The first two digits are width in feet and inches, and the second pair is height. A 3060 window is 3 feet 0 inches wide by 6 feet 0 inches tall.
Why does door rough opening height change with floor finish?
Carpet and pad typically need extra clearance, so the rule-of-thumb rough opening is often 2.5 inches taller instead of 2 inches.
Do skylights need engineered headers?
Many do. Always verify the exact framing detail and header requirement from the skylight manufacturer or project engineer.
Keep the project moving
Use the free calculator for fast takeoffs, then plug the result into a reusable field template.
Need templates? Browse our professional template store — contracts, checklists, and planners from $17.