Guides6 min readFloorGen team
Standard Window Sizes: Size Codes, Rough Openings and Egress
Standard window sizes in US homes: double-hung 24 to 48 in wide and 36 to 72 in tall, size codes like 3050, rough openings, egress, safety glass and a plan.
Standard window sizes in US homes run from about 24 to 48 in wide and 36 to 72 in tall for double-hung windows, the most common type, and makers name them with a four-digit code: 3050 means 3 ft 0 in wide by 5 ft 0 in tall. The code is a nominal size. The real unit is usually a little different, and the rough opening in the wall is about ½ in bigger than the unit, so always size the opening from the maker's chart. Bedroom windows also have to meet the escape-opening rule: at least 5.7 ft² clear, 24 in high, 20 in wide, and no more than 44 in off the floor.
Below are the common sizes, how to read a size code, rough openings, the code rules that limit size and placement (egress, safety glass, fall protection, daylight), and the windows of a real three-bedroom house plan. For doors, see standard door sizes.
Common window sizes
| Window type | Common widths | Common heights | Where it is used |
|---|---|---|---|
| Double-hung or single-hung | 24 to 48 in | 36 to 72 in | Bedrooms, living rooms, most of the house |
| Slider (gliding) | Varies by maker; usually wider than tall | Varies by maker | Basements, over counters, low walls |
| Casement | Varies by maker; usually taller than wide | Varies by maker | Over sinks, egress windows, modern houses |
| Picture (fixed) | Often made to order | Often made to order | Views; does not open, so no ventilation or egress |
Guides agree on the double-hung range but not on every step inside it; some list widths in 4 in steps (24, 28, 32 in and so on), others in larger ones. Casement and slider sizes vary more between makers, so take them from the chart of the line you choose.
How to read a window size code
A four-digit code gives the width in feet and inches, then the height in feet and inches: 2030 is 2 ft 0 in × 3 ft 0 in, 3050 is 3 ft 0 in × 5 ft 0 in, 2852 is 2 ft 8 in × 5 ft 2 in (32 × 62 in). Width always comes first. Some makers code in inches instead, and the code can refer to either the unit or the rough opening, depending on the maker.
The code is a name, not a measurement. In Andersen's 400 Series tilt-wash chart, for example, the unit sold as TW3052 measures 3 ft 1⅝ in × 5 ft 4⅞ in, and the chart lists its minimum rough opening as the unit size plus ½ in each way. Order from the chart, not the code.
Rough openings and window height
- Rough opening: the framed hole, usually about ½ in wider and taller than the unit, which leaves room to shim it plumb and seal it. The maker's chart gives the exact figure for each size.
- Head height: many builders line the tops of windows up with the tops of the doors, often 6 ft 8 in or a little higher on 8 ft walls. That is common practice, not code, but a façade looks calmer when heads line up.
- Sill height: set by the room. Over a kitchen counter the sill has to clear the 36 in counter and backsplash; in a bedroom it must be 44 in or lower for egress; a low sill on an upper floor brings in the fall protection rule below.
Code rules that limit window size
| Rule | What it requires | Section |
|---|---|---|
| Emergency escape opening | Every sleeping room: at least 5.7 ft² clear (5.0 ft² at grade), 24 in clear high, 20 in clear wide, sill no more than 44 in above the floor | R310 [R319] |
| Light and ventilation | Glazing of at least 8% of the room's floor area, and openable area of at least 4%, unless lighting and mechanical ventilation are provided instead | R303.1 |
| Safety glass by a door | Glazing within 24 in of a door edge whose bottom is less than 60 in above the floor | R308.4.2 [R324] |
| Safety glass in large panes | A pane over 9 ft² with its bottom less than 18 in and top more than 36 in above the floor, near a walking surface | R308.4.3 [R324] |
| Safety glass near a tub or shower | Glazing within 60 in of the water's edge whose bottom is less than 60 in above the standing surface | R308.4.5 [R324] |
| Window fall protection | Where the sill is less than 24 in above the floor and the opening more than 72 in above the ground outside, a limit on the opening or a fall prevention device | R312.2.1 [R321] |
The egress rule is about the clear opening, not the unit size, and the window type changes it a lot. A casement opens almost its full size; a double-hung opens only one sash, about half its height; a slider half its width. A double-hung bedroom window has to be roughly twice as tall as a casement to give the same clear height, which is why egress windows in basements are so often casements or sliders. Our guides to egress window requirements and legal bedroom requirements have the details.
The windows in a three-bedroom ranch
FloorGen's 3-bed ranch template, a 70 × 36 ft house with a two-car garage, uses five window widths. All are double-hung, 4 ft 3 in (130 cm) tall with the sill at about 35½ in (90 cm), except the two small bathroom windows, which are about 24 × 24 in and set high:
| Room | Windows (width × height) |
|---|---|
| Living room | Two 60 × 51 in |
| Dining room | One 60 × 51 in |
| Primary bedroom | One 60 × 51 in |
| Kitchen | One 48 × 51 in |
| Bedrooms 2 and 3 | One 48 × 51 in each, plus a 36 × 51 in on the east wall of bedroom 3 |
| Laundry and garage | One 30 × 51 in and one 36 × 51 in |
| Primary and hall baths | Small 24 × 24 in windows, sill about 55 in |
Every bedroom passes FloorGen's escape-opening check: a 48 × 51 in double-hung opens about half its height, roughly 48 × 25½ in or 8½ ft², well over the 5.7 ft² minimum, with a 35½ in sill. Change the same window to a casement and the check counts nearly the whole unit, about 17 ft². The daylight rule is closer: the primary bedroom has 266.1 ft² of floor and one 60 × 51 in window, about 21¼ ft² as a unit, right at the 8% line (21.3 ft²), and the glass itself is smaller than the unit, so a real design would enlarge it or add a second window.
Windows in FloorGen
Each window has a Window type (casement, double-hung, slider, awning, picture or tilt-and-turn), a width, a height and a Sill height. Under the IRC profile, FloorGen checks every bedroom for an escape opening, estimating the clear opening from the type, and flags a habitable room with no window at all. In the elevations, Façade notes point out windows whose heads or sills do not line up. It does not check the 8% glazing ratio, safety glass or fall protection, and its clear opening is an estimate from the overall size, so confirm the net clear opening from the maker's egress data. More on drawing them in how to draw a floor plan.
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