The rough opening for a commercial door frame depends on the frame type. For drywall wrap-around frames, add 2 inches to the nominal door width and 1 inch to the nominal door height. For masonry frames, add 4-1/4 inches to the nominal door width and 2-1/8 inches to the nominal door height. These formulas account for the jamb and header material that occupies space within the opening. Getting the rough opening correct is a critical first step in ordering the right size door and frame assembly.
CDF Distributors’ ProBuilder tool at cdfdistributors.com calculates rough openings automatically for every frame configuration, displaying both nominal and exact dimensions on every quote. For assistance, call (855) 769-9895 or email sales@cdfdoors.com.
Rough Opening Formulas
All door sizes referenced in rough opening calculations are nominal sizes, not exact sizes. A nominal 3’0” x 7’0” door is referenced as 36” x 84” in calculations. The rough opening formula varies by frame type because each type occupies a different amount of space within the wall opening.
Drywall Wrap-Around Frames
Drywall frame jambs and headers are 2” wide, but because they wrap around the drywall edge, only 1” per jamb and 1” for the header projects into the opening. The formulas are:
- Rough Opening Width = Nominal Door Width + 1” (strike jamb) + 1” (hinge jamb) = Door Width + 2”
- Rough Opening Height = Nominal Door Height + 1” (header) = Door Height + 1”
Example: A 3’0” x 7’0” (36” x 84”) door in a drywall frame requires a rough opening of 38” wide by 85” tall.
Masonry Frames
Masonry frame jambs and headers are 2” wide and do not wrap the opening. CDF recommends adding 1/8” of wiggle room to each jamb and the header to ease installation into block or concrete walls. The formulas are:
- Rough Opening Width = Nominal Door Width + 2” (strike jamb) + 1/8” + 2” (hinge jamb) + 1/8” = Door Width + 4-1/4”
- Rough Opening Height = Nominal Door Height + 2” (header) + 1/8” = Door Height + 2-1/8”
Example: A 3’0” x 7’0” (36” x 84”) door in a masonry frame requires a rough opening of 40-1/4” wide by 86-1/8” tall.
A 4” masonry header is available but is not widely used. If a 4” header is specified, adjust the height formula accordingly: Door Height + 4” + 1/8”.
Welded Frames
Welded hollow metal frames follow the same rough opening formulas as masonry frames when set into masonry or concrete openings, or the same formulas as drywall frames when used in stud wall applications. The frame type and wall construction determine the formula, not whether the frame corners are welded or knocked down.
Wall Thickness Matching
The frame depth must match the wall thickness exactly. A mismatch between frame depth and wall thickness cannot be corrected during installation. Before ordering, measure the total wall thickness including all finish layers. Common configurations include metal studs with 5/8” sheetrock on each side (4-7/8” total) and CMU block walls of various widths.
Measure wall thickness in at least two locations within the rough opening. Construction tolerances can cause variations, especially in metal stud walls. CDF’s ProBuilder displays the frame depth for every configuration, allowing verification against field measurements before placing an order.
How to Measure a Rough Opening
Accurate rough opening measurements prevent ordering errors and installation problems. Follow these steps to verify a rough opening before ordering.
- Measure width at the top and bottom of the opening. Record the narrower measurement.
- Measure height on the left side and right side of the opening. Record the shorter measurement.
- Measure wall thickness at the top, middle, and bottom of the opening on both sides. Confirm consistency.
- Check that the opening is plumb and square. Use a level on both jamb locations and a tape measure diagonally corner to corner. Equal diagonal measurements confirm a square opening.
Metal stud walls can shift during construction, so verifying measurements at multiple points within the opening is necessary. An out-of-spec opening will cause problems throughout the entire frame installation.
Finding Door and Frame Size from a Rough Opening
When the rough opening already exists and the door size needs to be determined, reverse the formulas above. This is common in renovation and tenant improvement projects where the wall is already built.
Drywall Frame Reverse Formulas
- Nominal Door Width = Rough Opening Width − 2”
- Nominal Door Height = Rough Opening Height − 1”
Masonry Frame Reverse Formulas
- Nominal Door Width = Rough Opening Width − 4-1/4”
- Nominal Door Height = Rough Opening Height − 2-1/8”
Example: A rough opening measuring 38” wide by 85” tall in a drywall stud wall requires a 36” x 84” (3’0” x 7’0”) door and drywall frame assembly.
Rough Opening Reference Table by Door Size
The following table lists the required rough opening dimensions for standard commercial door sizes in both drywall wrap-around frames and masonry frames. Drywall frame rough openings add 2” to width and 1” to height. Masonry frame rough openings add 4-1/4” to width and 2-1/8” to height (including 1/8” wiggle room per jamb and header). All door sizes shown are nominal.
Nominal Door Size | Door Width x Height | Drywall Frame RO (W x H) | Masonry Frame RO (W x H) |
2’0” x 6’8” | 24” x 80” | 26” x 81” | 28-1/4” x 82-1/8” |
2’6” x 6’8” | 30” x 80” | 32” x 81” | 34-1/4” x 82-1/8” |
2’8” x 6’8” | 32” x 80” | 34” x 81” | 36-1/4” x 82-1/8” |
3’0” x 6’8” | 36” x 80” | 38” x 81” | 40-1/4” x 82-1/8” |
2’0” x 7’0” | 24” x 84” | 26” x 85” | 28-1/4” x 86-1/8” |
2’6” x 7’0” | 30” x 84” | 32” x 85” | 34-1/4” x 86-1/8” |
2’8” x 7’0” | 32” x 84” | 34” x 85” | 36-1/4” x 86-1/8” |
3’0” x 7’0” | 36” x 84” | 38” x 85” | 40-1/4” x 86-1/8” |
3’6” x 7’0” | 42” x 84” | 44” x 85” | 46-1/4” x 86-1/8” |
4’0” x 7’0” | 48” x 84” | 50” x 85” | 52-1/4” x 86-1/8” |
3’0” x 8’0” | 36” x 96” | 38” x 97” | 40-1/4” x 98-1/8” |
3’6” x 8’0” | 42” x 96” | 44” x 97” | 46-1/4” x 98-1/8” |
4’0” x 8’0” | 48” x 96” | 50” x 97” | 52-1/4” x 98-1/8” |
Rough Openings for Pair (Double Door) Configurations
For pair openings with two equal-width doors, double the single-door width before applying the rough opening formula. The height formula remains the same.
- Drywall Frame Pair RO Width = (2 x Nominal Door Width) + 2”
- Masonry Frame Pair RO Width = (2 x Nominal Door Width) + 4-1/4”
Example: A pair of 3’0” x 7’0” doors (72” combined width) in a drywall frame requires a rough opening of 74” wide by 85” tall. The same pair in a masonry frame requires 76-1/4” wide by 86-1/8” tall.
Rough Openings and Fire-Rated Assemblies
The rough opening formulas above apply equally to standard and fire-rated assemblies. Fire rating does not change the rough opening dimensions. However, fire-rated assemblies require that the door, frame, and all hardware carry matching fire labels. CDF fabricates fire-rated assemblies at all five standard rating levels: 20-minute, 45-minute, 60-minute, 90-minute, and 3-hour. Drywall frames are available up to 90 minutes; assemblies requiring a 3-hour rating must use masonry frames.
Verify all fire rating requirements with project specifications and the Authority Having Jurisdiction (AHJ).
Configure Your Assembly
CDF’s ProBuilder tool at cdfdistributors.com allows contractors and facility managers to configure complete door and frame assemblies online. ProBuilder automatically calculates the required rough opening for every configuration and displays both nominal and exact dimensions on every quote. During configuration, door, frame, and hardware selections are structured as a complete assembly with compatible options and instant pricing.
For assistance determining rough opening requirements or configuring an assembly, call (855) 769-9895 or email sales@cdfdoors.com. CDF’s sales team is available Monday through Friday, 7:30 AM to 4:30 PM CT.
Frequently Asked Questions
What is the rough opening formula for a drywall wrap-around frame?
Add 2 inches to the nominal door width and 1 inch to the nominal door height. Drywall frame jambs and headers are 2” wide, but because they wrap around the drywall edge, only 1” per jamb and 1” for the header projects into the opening. CDF’s ProBuilder calculates this automatically for every configuration.
What is the rough opening formula for a masonry frame?
Add 4-1/4 inches to the nominal door width and 2-1/8 inches to the nominal door height. This includes the 2” jamb and header material plus 1/8” of wiggle room on each jamb and the header to ease installation into block or concrete walls.
Why are door sizes called nominal?
Nominal door sizes refer to the standard designation used in the industry, such as 3’0” x 7’0”. The exact (actual) door dimensions differ slightly from the nominal size. When calculating rough openings, always use the nominal size in the formulas. The exact size matters for manufacturing tolerances and clearances, but the rough opening is based on the nominal designation.
What happens if the rough opening is too large?
A rough opening that is too wide leaves excessive gaps between the frame and the wall structure. In drywall frames, this can compromise the compression anchor function, resulting in a frame that is not secure. In masonry frames, excessive gaps require additional grouting or shimming to stabilize the frame.
What happens if the rough opening is too small?
A rough opening that is too narrow prevents the frame from being inserted into the wall. The opening must be enlarged before the frame can be installed, which adds time and cost to the project.
Does the rough opening change for fire-rated assemblies?
No. The rough opening formulas are the same for standard and fire-rated assemblies. Fire rating affects the door, frame, and hardware specifications, not the rough opening dimensions. CDF fabricates fire-rated assemblies at all five standard rating levels: 20-minute, 45-minute, 60-minute, 90-minute, and 3-hour.
How do I find the door size if I already have a rough opening?
Reverse the formula. For a drywall frame, subtract 2” from the rough opening width and 1” from the height to get the nominal door size. For a masonry frame, subtract 4-1/4” from the width and 2-1/8” from the height. CDF’s ProBuilder and the CDF sales team can assist with reverse calculations.
What is the rough opening for a pair of doors?
Double the single-door nominal width, then apply the standard formula. For example, a pair of 3’0” doors have a combined nominal width of 72”. In a drywall frame, the rough opening width is 74”. In a masonry frame, the rough opening width is 76-1/4”. The height formula remains the same as for a single door.
About This Guide
This reference guide reflects CDF Distributors’ standard rough opening specifications used in commercial door and frame fabrication. The formulas and dimensions are consistent with industry practice for hollow metal frames installed in drywall stud walls and masonry construction. CDF Distributors fabricates and ships complete door and frame assemblies from its Nashville, Tennessee headquarters.
For questions about rough opening requirements or to configure a door and frame assembly, contact CDF at (855) 769-9895 or sales@cdfdoors.com. Configure your assembly online at cdfdistributors.com using ProBuilder.
