Walk into any Andersen or Pella showroom and you quickly learn there is no single answer to how big is a standard window. Manufacturers produce dozens of stock sizes, and the right one depends on the room, the wall framing, and local building code minimums. The most common residential window in the US measures 36 inches wide by 48 inches tall, but bathrooms, basements, and kitchens often run smaller. This guide breaks down the actual stock dimensions used by Andersen 400 Series, Pella Lifestyle, Marvin Essential, and Milgard Tuscany, plus the rough opening sizes you need before ordering.
Why Window Sizes Are Not Truly Standard
Each manufacturer keeps its own dimension chart. Andersen lists windows by call size in a coded format like 2842, which means 2 feet 8 inches wide by 4 feet 2 inches tall. Pella uses similar coding. Custom sizing is available on most lines but adds 15 to 30 percent to the price and 4 to 8 weeks to lead time.
Stock sizes exist because rough openings in 2×4 and 2×6 wall framing are easier to build at 16-inch or 24-inch on-center stud spacing. A window that fits naturally between studs without re-framing saves the builder hours and the homeowner several hundred dollars per opening.
Standard Double-Hung Window Sizes
Double-hung windows are the most common style in American homes. Both sashes slide vertically and the unit fits a wide range of openings. Typical stock widths range from 24 inches to 48 inches, and heights from 36 inches to 72 inches.
- 24 by 36 inches: small bedroom or bathroom
- 28 by 54 inches: standard secondary bedroom
- 36 by 48 inches: most common living room or dining room
- 36 by 60 inches: tall living room or stairwell
- 48 by 60 inches: large master bedroom or great room
Rough openings run roughly half an inch larger than the unit dimension on each side to allow for shimming and insulation. Always confirm with the manufacturer spec sheet before framing.
Picture Window Dimensions
Picture windows are fixed glass panels with no operating sash. Because they do not need to open, manufacturers produce them in much larger sizes. Common stock widths span 24 to 96 inches, and heights from 12 to 72 inches.
Large picture windows over 48 inches in either direction usually require tempered safety glass under IRC R308.4 because of impact-zone proximity to floors and doors. Tempered glass adds roughly 20 to 30 percent to the cost but is mandatory in most jurisdictions for spans this large.
Casement and Awning Window Sizes
Casement windows hinge on the side and crank outward. Awning windows hinge at the top and tilt outward. Both styles seal tighter than double-hung units and earn higher energy ratings, often hitting U-factors below 0.27 with Low-E coatings.
Standard casement widths run 14 to 35 inches, with heights from 24 to 72 inches. Awning windows tend to be wider than tall, commonly 24 to 48 inches wide and 16 to 36 inches tall. Marvin Essential and Andersen 400 Series both make these in increments that match standard framing.
Bathroom and Egress Window Codes
Bathroom windows often run smaller for privacy and wall space, typically 24 by 36 inches or 28 by 42 inches. IRC R303.3 requires either an openable window with at least 3 square feet of area or a mechanical ventilation fan rated at 50 CFM minimum.
Bedroom egress windows have strict size minimums under IRC R310. The minimum net clear opening must be at least 5.7 square feet, with a minimum opening width of 20 inches and a minimum opening height of 24 inches. The sill cannot sit higher than 44 inches above the finished floor. A standard 36 by 60 inch double-hung often satisfies these requirements, but verify with local code officials before ordering.
Kitchen and Garden Window Sizes
Kitchen windows above the sink usually measure 36 to 48 inches wide and 36 to 42 inches tall. The lower edge typically sits 36 to 42 inches off the finished floor to clear standard counters and backsplashes.
Garden windows, which project outward to create a shelf for herbs or plants, range from 36 to 60 inches wide and 36 to 48 inches tall, with a projection of 16 to 20 inches. These units are heavier and require additional structural support. Pella and Andersen both make stock garden windows that drop into standard rough openings with the right header.
Rough Opening Sizes
The rough opening is the framed hole in the wall where the window sits. For a unit listed as 36 by 48 inches, the rough opening typically measures 36 and a half inches wide by 48 and a half inches tall, giving a quarter inch of shim space on each side. Andersen, Pella, and Marvin each publish exact rough opening dimensions per model.
Header sizing matters in load-bearing walls. A 4-foot opening in a single-story wall usually calls for a double 2×6 header. Wider openings or two-story walls may need engineered LVL beams. Consult your local code or a structural engineer for openings over 6 feet wide.
Replacement vs New Construction Windows
Replacement windows, sometimes called insert windows, slip inside the existing frame without removing siding or interior trim. These are sized to fit the existing opening minus the old sash and balance, so the glass area is slightly smaller than the original.
New construction windows include a nailing fin and are installed during framing or full siding replacement. They give a tighter weather seal but require more invasive installation. Andersen 400 Series and Pella Architect Series both come in either configuration. Expect to pay $400 to $1,200 per opening installed for stock-size double-hung units, more for casement or custom sizes. With these dimensions in hand, you now know how big is a standard window across every common room and code situation.
