Standard Window Sizes: Chart by Type, Rough Openings and Egress Rules
Standard sizes for double-hung, sliding, casement, picture and basement windows in inches and centimeters, how to read the four-digit size code, and the minimum sizes building codes require for bedroom windows.
Most US residential windows are 24 to 48 in wide (61 to 122 cm) and 36 to 72 in tall (91 to 183 cm). Sizes go up in 2 to 4 in steps and are written as a code of width then height in feet and inches, so a 3050 window is 3 ft 0 in × 5 ft 0 in (36 × 60 in, 91 × 152 cm).
- Double-hung width
- 24 to 48 in
- Double-hung height
- 36 to 72 in
- Rough opening
- Unit + 1/2 in
- Egress opening
- 5.7 sq ft min
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Standard window sizes by type
There is no national standard that fixes window sizes, but US manufacturers build their stock lines on the same grid of widths and heights. The ranges below cover the stock sizes of the major brands; anything outside them is usually a custom order.
| Window type | Widths (in) | Heights (in) | Widths (cm) | Heights (cm) |
|---|---|---|---|---|
| Double-hung / single-hung | 24 to 48 | 36 to 72 | 61 to 122 | 91 to 183 |
| Sliding (horizontal) | 36 to 84 | 24 to 60 | 91 to 213 | 61 to 152 |
| Casement | 14 to 36 | 24 to 72 | 36 to 91 | 61 to 183 |
| Awning | 24 to 48 | 20 to 36 | 61 to 122 | 51 to 91 |
| Picture (fixed) | 24 to 96 | 12 to 96 | 61 to 244 | 30 to 244 |
| Basement hopper | 32 | 14 to 24 | 81 | 36 to 61 |
| Bay / bow | 60 to 120 overall | 36 to 72 | 152 to 305 | 91 to 183 |
Casements stay narrow because a wide sash hanging on one side would sag and catch the wind. When an opening is wider than about 36 in, casements are combined in pairs or flank a fixed picture window. Sliders are the reverse: wide and low, which suits spaces over kitchen counters and in bedrooms where the sill needs to be high.
Common double-hung window sizes
Double-hung and single-hung windows make up the bulk of replacement orders in the US. These are the sizes builders use most often, with their size codes.
| Code | Size (in) | Size (cm) | Unit area | Typical location |
|---|---|---|---|---|
| 2030 | 24 × 36 | 61 × 91 | 6 sq ft (0.56 m²) | Bathrooms, stair landings |
| 2436 | 28 × 42 | 71 × 107 | 8.2 sq ft (0.76 m²) | Bathrooms, small bedrooms |
| 2846 | 32 × 54 | 81 × 137 | 12 sq ft (1.11 m²) | Bedrooms |
| 3050 | 36 × 60 | 91 × 152 | 15 sq ft (1.39 m²) | Bedrooms, living rooms |
| 3056 | 36 × 66 | 91 × 168 | 16.5 sq ft (1.53 m²) | Living rooms with 9 ft ceilings |
| 3462 | 40 × 74 | 102 × 188 | 20.6 sq ft (1.91 m²) | Tall windows, two-story rooms |
Unit area is the nominal size. The glass you see through is noticeably smaller: frames and sashes take roughly 2 to 3 in on each side, and a double-hung window loses more at the meeting rail. Energy codes and daylight rules use the glazed area from the manufacturer's spec sheet.
How to read window size codes
A four-digit window code gives width then height, each as feet and inches. 3050 reads as 3'0" × 5'0", or 36 × 60 in. 2846 reads as 2'8" × 4'6", or 32 × 54 in. Width always comes first, which matters for a slider, where 6040 (72 × 48 in) and 4060 (48 × 72 in) are very different windows.
The code is a nominal size. The actual frame is usually about 1/2 in smaller in each direction (a 3050 might measure 35 1/2 × 59 1/2 in), and the rough opening is the nominal size or slightly larger. Some brands use their own systems: codes that describe the rough opening, the glass, or a catalog number unrelated to inches. Always confirm the "unit dimension" and "rough opening" columns in the brand's catalog.
Rough opening vs window size
For new-construction and full-frame replacement, the framed opening should be about 1/2 in wider and 1/2 in taller than the window unit. That leaves roughly 1/4 in on each side for shims, levelling and insulating foam. Some manufacturers specify 3/4 in; their installation sheet is the authority.
| Window unit (in) | Rough opening (in) | Rough opening (cm) |
|---|---|---|
| 23 1/2 × 35 1/2 | 24 × 36 | 61 × 91.4 |
| 31 1/2 × 53 1/2 | 32 × 54 | 81.3 × 137.2 |
| 35 1/2 × 59 1/2 | 36 × 60 | 91.4 × 152.4 |
| 71 1/2 × 47 1/2 (slider) | 72 × 48 | 182.9 × 121.9 |
Measuring for an insert (pocket) replacement
- Measure the width between the side jambs at the top, middle and bottom of the opening, inside the existing frame.
- Measure the height from the top jamb to the sill at the left, center and right.
- Take the smallest of each set and subtract about 1/4 in from each to get the insert size. Many window companies make this deduction themselves, so say clearly if your figures are opening sizes or unit sizes.
- Check square. Measure both diagonals. If they differ by more than about 1/4 in, the frame is out of square and the insert must be sized to the tightest point.
Egress window size requirements for bedrooms
Every sleeping room and every habitable basement needs an emergency escape and rescue opening under IRC Section R310. The rules apply to the open area you can climb through, not the frame size, and many jurisdictions amend them, so confirm with your local building department.
The minimum width and height do not add up to the minimum area: 20 × 24 in is only 480 sq in (3.3 sq ft), while 5.7 sq ft is 821 sq in. With a 20 in clear width you need about 41 in of clear height, and with 24 in of clear height you need about 34 in of clear width.
| Window | Approximate opening | Typical result |
|---|---|---|
| Casement, 24 × 48 in | About 20 × 44 in clear (6.1 sq ft) | Passes; casements open almost fully |
| Double-hung, 36 × 60 in | About 32 × 26 in clear (5.8 sq ft) | Passes, barely; only the lower sash opens |
| Double-hung, 32 × 54 in | About 28 × 23 in clear (4.5 sq ft) | Fails: too small and under 24 in high |
| Slider, 48 × 48 in | About 21 × 44 in clear (6.4 sq ft) | Passes; only one panel opens |
Clear openings in the table are estimates; manufacturers publish the exact net clear opening for each size, and many catalogs flag which sizes meet egress. Below-grade egress windows need a window well of at least 9 sq ft with a projection and width of at least 36 in, and a permanent ladder or steps if the well is deeper than 44 in.
Where a window sill is less than 24 in above the floor and more than 72 in above the ground outside, the IRC (R312.2) requires an opening limiter or guard so a 4 in sphere cannot pass through, unless the window is an egress window fitted with a releasable device.
Window height and placement
- Head height: windows are usually set so their tops line up with the door heads, about 80 in above the finished floor in rooms with 8 ft ceilings and 96 in in rooms with 9 to 10 ft ceilings.
- Sill height: with an 80 in head, a 60 in tall window puts the sill at 20 in, a 54 in window at 26 in and a 48 in window at 32 in. Kitchen windows over a 36 in counter usually start at about 42 in to clear the backsplash.
- Bathrooms: sills of 60 in or more give privacy without frosted glass, which usually means a short slider or awning.
Covering the window afterwards? Measure after installation, then use our guides to blind sizes, curtain sizes and curtain rod lengths.
Frequently asked questions
What does a window size code like 2436 mean?
The first two digits are the width in feet and inches and the last two the height: 2436 is 2 ft 4 in × 3 ft 6 in, or 28 × 42 in. Some brands use their own codes that refer to the rough opening or glass size, so check the catalog's dimension table before ordering.
What size is a 1 square meter window?
A window of 1 m² (10.76 sq ft) is, for example, 1,000 × 1,000 mm (39.4 × 39.4 in) or 800 × 1,250 mm (31.5 × 49.2 in). In US terms, a 36 × 48 in window is close at 1,728 sq in, or 1.11 m².
How big is a standard patio window or sliding patio door?
Sliding patio doors are sold as 5, 6 and 8 ft wide units (about 60, 72 and 96 in) by 80 in tall, with frames about 1/2 in smaller than the nominal size. Large picture windows beside patios are commonly 48 to 96 in wide. See our door sizes guide for patio door rough openings.
How high off the floor should a window be?
Window heads are usually aligned with door heads at about 80 in above the floor, which puts the sill of a 48 in tall window at about 32 in. Bedroom egress sills may be no more than 44 in above the floor, and the IRC requires fall protection when a sill is under 24 in above the floor and more than 72 in above the ground outside.
Do windows come in standard sizes in the UK?
UK windows are mostly made to measure, so there is no single standard. Replacement frames are typically ordered 10 mm smaller than the brick opening in each direction to leave a fitting gap that is then sealed.