What is the rough opening for a 36x48 window?
36½″ × 48½″
The short answer
A 36 × 48 inch window usually needs a rough opening of 36½″ wide by 48½″ tall. That half inch in each direction lets the installer level the window, shim it and seal it properly. Window sizes are named differently by each maker, so check their rough opening figure before framing.
How it is worked out
- Window unit: 36″ × 48″
- Add ½″ to the width: 36½″
- Add ½″ to the height: 48½″
Other sizes and options
| Window size | Rough opening |
|---|---|
| 24″ × 36″ | 24½″ × 36½″ |
| 30″ × 48″ | 30½″ × 48½″ |
| 36″ × 48″ | 36½″ × 48½″ |
| 36″ × 60″ | 36½″ × 60½″ |
| 48″ × 48″ | 48½″ × 48½″ |
| 60″ × 48″ | 60½″ × 48½″ |
What can change the amount?
Replacement windows that fit inside an existing frame are measured differently: measure inside the old frame at three points and use the smallest. New construction windows follow the rough opening rule above.
Plan your windowsRoomveil opens with these measurements filled in. Change them to match your room, see the result on a photo, and get the exact amount. Free, no sign-up.Open in Roomveil
Worked out with common rules of thumb and code minimums, for planning. Check the product label, the maker's instructions and your local building code before you buy or build. More detail in the Window and door sizes guide.