Door Sizes Guide: Standard Interior & Exterior Dimensions

Understanding Door Sizes and Standards

Why Door Sizes Are Standardized

Door standardization emerged from practical necessity in the construction industry. Before standardization, every door was custom-made, requiring skilled carpenters to build frames and doors on-site. This made construction slow, expensive, and inconsistent. The introduction of standard door sizes in the early 20th century revolutionized home building by enabling mass production of pre-hung doors, reducing costs, and ensuring consistent quality.

Today's standard door sizes reflect decades of refinement based on ergonomics, building codes, furniture dimensions, and accessibility requirements. The ubiquitous 36-inch-wide by 80-inch-tall exterior door, for example, provides adequate clearance for furniture moving while fitting within standard wall framing (which uses 2×4 or 2×6 studs with typical ceiling heights). These standards also simplify renovations and door replacements, as homeowners can purchase stock doors that fit existing openings without custom fabrication.

Interior Door Dimensions Explained

The most common interior door widths are 28, 30, and 32 inches, with 30 inches being the standard for bedrooms and bathrooms. The 24-inch width is typically reserved for closets, pantries, and utility spaces where full human passage isn't the primary function. The 32-inch width is increasingly popular for master bedrooms and as a general standard in new construction because it provides better accessibility and a more substantial appearance.

Interior door height standardized at 80 inches (6 feet 8 inches) for homes with 8-foot ceilings—the most common ceiling height in residential construction from the mid-20th century. This 80-inch height provides adequate clearance for people passing through (even those over 6 feet tall) while leaving room for the door frame and floor clearance. With modern homes featuring 9-foot or 10-foot ceilings, 96-inch (8-foot) doors are becoming more popular, creating a more proportional appearance and grander feel.

Exterior Door Considerations

Exterior doors differ from interior doors in several key ways. The standard 36-inch width for exterior entry doors is mandated by many building codes because it ensures furniture and appliances can be moved in and out of the home. Try moving a refrigerator, couch, or mattress through a 30-inch door—it's challenging or impossible in many cases. The 36-inch width provides the necessary clearance for these large items while still fitting within standard wall framing.

The increased thickness of exterior doors (1¾ inches versus 1⅜ inches for interior) provides enhanced structural integrity, better insulation, improved sound dampening, and more secure anchoring for deadbolts and other locking mechanisms. This extra thickness also allows for more substantial weatherstripping, creating better seals against drafts and water intrusion. Premium exterior doors may be even thicker, up to 2¼ inches, especially in custom or high-security applications.

Rough Opening Mathematics

Understanding rough opening dimensions is crucial for new construction and renovations. The rough opening must accommodate not just the door slab itself, but also the door jamb (the frame), installation shims for leveling and plumbing, and small adjustments during installation. The standard formula adds 2 inches to the door width and 2½ inches to the door height, though this can vary based on the specific pre-hung door unit.

For example, a 30-inch door requires a 32-inch rough opening width. This breaks down as: 30 inches for the door, approximately 1¾ inches for the jamb on both sides, and the remaining space for shims and adjustment. The height calculation adds 2½ inches to accommodate the head jamb at the top, floor clearance at the bottom, and shimming space. Pre-hung doors (doors already mounted in a frame) typically come with manufacturer specifications for rough opening dimensions, which should always be followed precisely.

ADA Compliance and Accessibility

The Americans with Disabilities Act (ADA) transformed door sizing requirements by establishing minimum accessibility standards. The critical measurement is the "clear opening width"—the actual passable width when the door is open at 90 degrees. This must be at least 32 inches for ADA compliance. A standard 36-inch door provides approximately 33-34 inches of clear opening when accounting for the door's thickness and the stop on the jamb, making it the minimum practical size for ADA-compliant doorways.

ADA requirements extend beyond width to include maneuvering clearances on both sides of the door, maximum opening force requirements (no more than 5 pounds of force for interior, non-fire-rated doors), threshold height limitations, and hardware specifications. Door handles must be lever-style or other designs operable with one hand without tight grasping, pinching, or wrist twisting. These requirements aren't just for commercial buildings—they're increasingly incorporated into residential design through universal design principles that make homes more accessible to people of all ages and abilities.

Regional and International Variations

While this guide focuses on US standards, door sizes vary internationally. European doors commonly use metric dimensions, with standard sizes like 70 cm, 80 cm, and 90 cm widths (approximately 28", 31.5", and 35.5"). Heights commonly range from 200 cm to 210 cm (approximately 79" to 83"). British door standards differ slightly from both US and continental European standards, with common widths of 762mm (30") and 838mm (33").

Australian door standards generally follow measurements similar to the US, with common widths of 820mm (32.3") and 870mm (34.3"). Canadian standards closely mirror US standards due to integrated building supply chains and similar building codes. When sourcing doors internationally or working with imported doors, careful attention to dimensional standards and hardware compatibility is essential to avoid costly mistakes.

Door Swing and Clearance

Door sizing must account for swing clearance—the space required for the door to open fully. Most interior doors swing inward into rooms, requiring clear floor space within the room for the door's arc. A 36-inch door swinging 90 degrees requires approximately 36 inches of clearance depth from the doorway. Building codes typically require doors to swing in the direction of egress (exit travel) for safety, though this primarily applies to commercial buildings and certain residential applications.

Floor clearance is equally important. Standard practice leaves ½ to ¾ inch between the bottom of the door and the finished floor to allow the door to swing freely over carpeting or floor irregularities. Too little clearance causes binding; too much creates drafts and looks unprofessional. When installing new flooring, doors may need to be trimmed or re-hung to maintain proper clearance. Pocket doors and sliding barn doors avoid the floor clearance issue by riding on overhead tracks, though they require wall space or surface mount hardware respectively.

Double Doors and Wide Openings

Double doors create wider openings by using two door slabs within a single frame. The most common configuration uses two 36-inch doors to create a 72-inch opening, popular for main entries, master bedroom suites, and formal dining rooms. Double doors can be paired (both doors operational) or have one door fixed with flush bolts, with only the active door used regularly and the fixed door opened only when full width access is needed.

French doors are a specific style of double doors featuring multiple glass panes, used primarily for patio or garden access where natural light is desired. Sliding patio doors offer an alternative to swinging French doors, providing wide openings without requiring clearance for door swing. Standard sliding patio doors are 72 inches wide (with one 36-inch fixed panel and one sliding 36-inch panel), though wider configurations up to 144 inches exist for expansive openings.

Specialty Door Types

Barn doors have surged in popularity for both rustic and modern interiors. These sliding doors mount on exterior tracks above the doorway, requiring no floor track but needing adequate wall space (typically twice the door width) beside the opening for the door to slide fully open. The hardware mounts 6-8 inches above the door height, requiring sufficient wall and ceiling clearance. Barn doors work well for closets, bathrooms, and pantries where swing clearance is limited, though they provide less sound and light isolation than traditional hinged doors.

Pocket doors slide into a recessed cavity within the wall, completely disappearing when open. They're ideal for tight spaces like small bathrooms where door swing would be problematic. However, pocket doors require planning during framing—the wall must accommodate a pocket frame that's roughly twice the door width plus 2 inches. This precludes placing electrical outlets or switches on that wall section and makes future access to plumbing or wiring within the pocket wall difficult. Despite these limitations, pocket doors excel at maximizing usable floor space in compact areas.

Material, Construction, and Cost Implications

Door construction significantly impacts cost, durability, and appearance. Hollow-core doors, common for interior applications, consist of a thin veneer over a lightweight honeycomb core. They're inexpensive ($30-$80) but offer minimal sound insulation and are easily damaged. Solid-core doors use a solid composite or engineered wood core with veneer or laminate facing, providing better sound dampening, greater durability, and a more substantial feel ($100-$300). True solid wood doors, milled from hardwoods like oak, maple, or mahogany, are premium options ($300-$1,000+) offering superior durability, beauty, and sound isolation.

Exterior doors require weather-resistant construction. Steel doors offer excellent security and energy efficiency at moderate cost ($200-$600). Fiberglass doors mimic wood grain while providing superior insulation and weather resistance ($500-$1,500). Solid wood exterior doors are premium options ($1,000-$5,000+) offering classic beauty but requiring regular maintenance. The door size directly impacts cost—wider doors, taller doors, and double door configurations increase material costs proportionally, while standard sizes benefit from mass production economies.

Installation Considerations

Pre-hung doors (door slab already mounted in a frame) simplify installation but require precise rough opening dimensions. Slab-only doors are cheaper but require mounting in an existing frame or building a new frame—a more complex installation requiring carpentry skills. When replacing doors, measuring the existing frame determines whether you need a standard size or custom door. Always measure width, height, and thickness at multiple points, as older homes may have settled or shifted, creating non-square openings.

Professional installation typically costs $150-$400 per door depending on complexity, location, and whether it's interior or exterior. DIY installation is feasible for those with basic carpentry skills and tools (level, shims, drill, saw), though exterior door installation is more challenging due to weatherproofing requirements. Poor installation can cause doors to bind, gaps to form, and locks to malfunction, so professional installation often proves worthwhile, especially for expensive doors or exterior applications where weatherproofing is critical.