Molding Frame Size Calculator for Doors
The right molding frame size for doors is vital to both the aesthetics and functionality of interior and exterior door installations. Properly sized and installed molding frames ensure doors fit correctly, look polished, and provide insulation and security. This comprehensive 2000-word guide covers everything you need to know, including common sizes, how to measure, rough opening calculations, types of molding profiles, installation tips, and detailed tables for easy reference.
1. Understanding Door Molding Frame Size
Door molding frames (also known as door casings or brickmoulds) are the trim that surrounds and finishes the door frame. They cover the gap between the door jamb and the wall or siding and are essential for both appearance and sealing against drafts.
Core Elements:
- Door Frame Size: The overall dimensions of the frame including the molding.
- Opening Size: The rough opening in the wall prepared to fit the door/frame assembly.
- Molding Width: The visible trim width around the door.
- Frame Depth: Thickness of the jamb and molding matching wall thickness.
Correct sizing balances fit and allows for appropriate sealing, insulation, and finish.
2. Standard Door Sizes and Frame Dimensions
Door sizes are most commonly defined by height x width (e.g., 80" x 36"). Frames and moldings then are sized to accommodate these door panel sizes plus proper clearance.
| Door Panel Width | Door Panel Height | Typical Frame Width | Typical Frame Height | Standard Brickmould (Molding) Width |
|---|---|---|---|---|
| 30" | 80" | 31.5" – 32" | 82" – 83" | 1.5" – 2" |
| 32" | 80" | 33.5" – 34" | 82" – 83" | 1.5" – 2" |
| 36" | 80" | 37.5" – 38" | 82" – 83" | 1.5" – 2" |
| 42" | 80" | 43" – 44" | 82" – 83" | 1.5" – 2" |
| 36" | 96" (8 feet) | 37.5" – 38" | 98" – 99" | 1.5" – 2" |
| 48" | 96" | 49.5" – 50.5" | 98" – 99" | 1.5" – 2" |
Source: Door manufacturers and installation guides
3. Rough Opening and Framing for Doors
The rough opening (RO) is the wall opening where the door frame will be installed. It must be larger than the door/frame unit to allow for shimming and adjustments.
Rough Opening Size Calculation:
- Rough Opening Width = Door Width + 2 inches
- Rough Opening Height = Door Height + 2.5 inches
For example, for a standard 36" x 80" door:
| Measurement Type | Dimension (inches) |
|---|---|
| Door Panel | 36 x 80 |
| Rough Opening Size | 38 x 82.5 |
This 2-inch wide and 2.5-inch tall margin allows room for:
- Shimming and leveling
- Insulation
- Clearance for door operation
4. Door Frame & Molding Profile Types
Various moldings fit around the door, each with different widths and decorative aspects:
| Molding Type | Description | Typical Width (inches) | Use Case |
|---|---|---|---|
| Brickmould (Brick Mould) | Exterior molding covering gap between door & siding | 1.5" – 2" | Exterior doors, weatherproof seal |
| Casing | Interior molding around door frame | 2" – 3" | Interior aesthetic finishing |
| Colonial | Traditional profile with curved edges | 2.25" – 3" | Classic style interior |
| Craftsman | Simple, square edges | 2" – 2.5" | Craftsman-style homes |
| Ornate / Victorian | Elaborate, decorative | 3" – 5" | Historic or custom interiors |
Choosing molding width depends on wall thickness and door style.
5. Measuring for Molding Frame Size: Step-by-Step
- Measure Door Panel width and height.
- Determine rough opening size, add 2" width and 2.5" height to door panel.
- Measure wall thickness because the jamb must extend past the drywall or siding.
- Select molding width to cover jamb and gap artistically.
- Confirm reveal size, the visible distance between door frame inside edge and molding outer edge, typically between 1/4" to 3/4".
6. Common Door Molding Frame Size Chart for Single Doors (6'8")
| Panel Size (in) | Frame Width (in) | Frame Height (in) | Brickmould Size (in) | Rough Opening Width Range (in) | Rough Opening Height Range (in) |
|---|---|---|---|---|---|
| 42" | 43.5" | 82.25" | 45.5" x 83.25" | 45" - 47" | 82.5" - 84" |
| 40" | 41.5" | 82.25" | 43.5" x 83.25" | 43" - 45" | 82.5" - 84" |
| 38" | 39.5" | 82.25" | 41.5" x 83.25" | 41" - 43" | 82.5" - 84" |
| 36" | 37.5" | 82.25" | 39.5" x 83.25" | 39" - 41" | 82.5" - 84" |
| 34" | 35.5" | 82.25" | 37.5" x 83.25" | 37" - 39" | 82.5" - 84" |
| 32" | 33.5" | 82.25" | 35.5" x 83.25" | 35" - 37" | 82.5" - 84" |
| 30" | 31.5" | 82.25" | 33.5" x 83.25" | 33" - 35" | 82.5" - 84" |
Source: Palma Door Systems
7. Frame Size and Wall Thickness Relationship
Frame sizes often include jamb depth options to match wall thickness. Common jamb depths:
| Wall Thickness (inches) | Common Jamb Depth (inches) | Notes |
|---|---|---|
| 4.5" | 4 9/16" | Common residential drywall + framing |
| 5.5" | 6" | Exterior walls with sheathing |
| 7" | 7 1/4" | Thicker walls/insulated walls |
Moldings overlap jamb edges for airtight seal and finishing coverage.
8. How to Choose the Right Molding Frame Size for Your Door
- Check your door panel size and rough opening dimensions.
- Measure wall thickness for jamb depth.
- Select molding width sufficient to cover the gap between jamb and wall.
- Match molding profile style to your door and interior/exterior décor.
- If replacing old molding, measure old width for compatibility or upgrade as desired.
9. Molding Frame Sizing Tips and Best Practices
- Always order doors with jambs matching your wall thickness for a flush look.
- Use adjustable jambs or shim gaps when wall thickness varies.
- Allow at least a 1/4" gap between door panel and jamb for clearance.
- Make sure brickmoulds overlap siding adequately for water protection.
- In rough openings, allow extra 2” width and 2-1/2” height for frame installation and shimming.
- Use seals/sweeps with door hardware to improve insulation.
10. Example Project: Framing a 36" x 80" Door with Brickmould
| Parameter | Dimension (inches) |
|---|---|
| Door panel size | 36" x 80" |
| Rough opening width | 38" (36" + 2") |
| Rough opening height | 82.5" (80" + 2.5") |
| Frame width | ~37.5" - 38" |
| Frame height | ~82.25" - 83.25" |
| Brickmould size | 39.5" x 83.25" |
| Wall thickness | 4 9/16" (standard) |
You’d order a door unit with a 37.5" wide jamb, ensure wall framing is ready at 38", then install brickmould sized 39.5" wide to cover siding edges smoothly.
11. Frequently Asked Questions
Q: What is brickmould and why is it important?
A: Brickmould is the exterior door frame molding that covers the gap between door frame and siding, essential for weatherproofing and aesthetics.
Q: Can I use interior casing molding outside?
A: No. Exterior brickmould needs to be weather-resistant and properly sealed.
Q: How much larger should the rough opening be than the door?
A: About 2 inches wider and 2.5 inches taller for shimming and adjustments.
Q: What molding width is best for thick walls?
A: Use wider molding (2" or more) or custom options to fully cover gaps and provide overlap.
12. Summary Table: Door Panel, Frame, and Rough Opening Sizes
| Door Panel (W x H) | Standard Frame Size (W x H) | Rough Opening Size (W x H) | Brickmould/Molding Size |
|---|---|---|---|
| 30" x 80" | 31.5" x 82.25" | 32" x 82.5" | 34" x 83.25" |
| 32" x 80" | 33.5" x 82.25" | 34" x 82.5" | 36" x 83.25" |
| 36" x 80" | 37.5" x 82.25" | 38" x 82.5" | 39.5" x 83.25" |
| 42" x 80" | 43.5" x 82.25" | 44" x 82.5" | 45.5" x 83.25" |
| 36" x 96" | 37.5" x 98" | 38" x 98.5" | 39.5" x 99.25" |
Conclusion
Correctly sizing your door molding frame is fundamental for a professional, weather-tight, and aesthetically pleasing door installation. By understanding door panel sizes, rough openings, wall thickness, and molding dimensions, you can ensure every door fits perfectly and complements your home design.
Use the tables and sizing guidelines provided as a solid foundation, confirm with measurements onsite, and consult manufacturer specs when ordering. Whether you are a DIY enthusiast, builder, or professional contractor, this guide equips you with the knowledge to frame doors accurately with the right molding size.