Manufacturers build replacement windows to a handful of industry-standard dimensions, and knowing those numbers saves hundreds in custom-order fees. Understanding common window sizes matters whether you are budgeting a whole-house replacement, ordering blinds, or planning a new-construction framing layout. This guide walks through the typical sizes for double-hung, casement, picture, and sliding windows, plus the rough opening math contractors use.
- How Window Sizes Are Written
- Standard Double-Hung Window Sizes
- Casement and Awning Dimensions
- Picture Window Sizes
- Sliding and Single-Hung Windows
- Egress Requirements by Room
- Typical Sizes by Room
- Replacement vs New Construction Windows
- Cost Ranges and Ordering Tips
- Measuring for Replacement Windows
- Energy Ratings and Glass Packages
How Window Sizes Are Written
The industry uses a four-digit code where the first two digits are width in feet and inches and the last two are height. A 2848 window is 2 feet 8 inches wide by 4 feet 8 inches tall, or 32 inches by 56 inches.
Listed dimensions typically refer to the window unit itself, not the rough opening. Rough opening is 1/2 to 3/4 inch larger on each side to allow shimming and insulation. Always confirm which measurement a quote references before ordering.
Standard Double-Hung Window Sizes
Double-hung windows account for roughly 60% of residential installations. Common widths: 24, 28, 32, 36, and 40 inches. Common heights: 36, 44, 52, 54, 60, and 72 inches.
Popular combinations include 2436 (bathroom), 3252 (bedroom), 3660 (living room), and 3672 (tall main rooms). A typical vinyl double-hung in 3252 costs $275 to $450 installed; in 3672 expect $400 to $650 installed.
Casement and Awning Dimensions
Casement windows crank outward and seal tighter than double-hungs, giving them better energy ratings. Standard widths run 14 to 36 inches in 2-inch increments; heights run 24 to 72 inches.
Awning windows hinge at the top and open outward from the bottom. They are wider than tall, commonly 24×20, 32×20, 36×24, and 40×30. Used in basements, bathrooms, and above kitchen sinks, awnings run $350 to $700 installed depending on glass package.
Picture Window Sizes
Picture windows do not open, maximizing glass area and view. Sizes range widely: 2 feet by 3 feet up to 8 feet by 6 feet. Common pairings with flanking casements use 4060 or 5060 center panels.
Because picture windows are fixed, they cost 20 to 30% less per square foot than operable windows of the same size. A 6040 vinyl picture window runs $500 to $900 installed.
Sliding and Single-Hung Windows
Horizontal sliders come in widths of 36, 48, 60, 72, and 84 inches, with heights of 24, 36, 48, and 60 inches. The 6048 slider is the most ordered size for bedrooms needing egress.
Single-hung windows look like double-hungs but only the bottom sash moves. Sizes mirror double-hung dimensions. They save $30 to $80 per unit and work well in rooms where top-sash operation is unnecessary.
Egress Requirements by Room
Every bedroom needs at least one window meeting IRC egress code: minimum 5.7 square feet of clear openable area (5.0 for ground floor), minimum 20-inch width, minimum 24-inch height, and sill no more than 44 inches above the floor.
A 3660 double-hung meets clear opening requirements when both sashes combine, but only if the individual open area hits 5.7 sq ft. Casement windows typically pass egress at smaller nominal sizes because the entire sash swings clear.
Typical Sizes by Room
Bathrooms: 2436 or 2828 obscure glass units for privacy. Bedrooms: 3252, 3660, or 6048 sliders for egress plus ventilation. Kitchens over sinks: 3636 casements or 4836 horizontal sliders.
Basements: small 3216 or 3224 hopper or slider units with well casing. Living rooms: 4060 or 6060 picture windows flanked by operable units. Garage service doors: often 3036 or small hopper windows at the top wall line.
Replacement vs New Construction Windows
Replacement (insert) windows slip into existing frames and are sized 1/4 inch smaller than the current window to fit. Measure the old window width at the top, middle, and bottom, then order to the smallest of the three.
New construction windows have nailing flanges and require rough-opening framing. Rough opening is typically 1/2 inch larger than window width and 1/2 inch larger than window height. Confirm by checking the manufacturer’s spec sheet for the exact model; variations of 1/4 inch are common between brands.
Cost Ranges and Ordering Tips
Expect vinyl replacement windows in standard sizes to cost $350 to $750 installed, fiberglass $600 to $1,200, and wood-clad $900 to $1,800. Custom sizes (any dimension not on a manufacturer’s stock list) add 15 to 30% to the unit price and 2 to 6 weeks to lead time.
When replacing all windows at once, measure every opening yourself before the estimator arrives. Discrepancies often turn up, especially in 1970s and earlier homes where on-site framing adjustments left openings varying by 1/2 inch or more within the same house.
Measuring for Replacement Windows
Measure width at three points inside the existing frame: top, middle, and bottom. Record the smallest number and subtract 1/4 inch for the replacement order. Do the same for height, measuring from the sill to the top of the frame on the left, center, and right sides.
Check for square by measuring diagonally corner to corner. If the two diagonals differ by more than 1/4 inch, the frame is racked and a standard insert will leak air. Budget $200 to $400 per opening for frame repair or full-frame replacement in those cases. Use a metal tape with a thumb-lock and verify once, then verify again a week later; homes settle and readings taken in summer humidity can shift 1/8 inch by winter.
Energy Ratings and Glass Packages
Window performance is measured by U-factor (insulation, lower is better) and SHGC (solar heat gain, lower reduces cooling load). ENERGY STAR minimums vary by climate zone: Northern homes should target U-factor under 0.27, Southern homes should prioritize SHGC under 0.25 even if U-factor is slightly higher.
Double-pane with low-E coating and argon gas fills most mid-range windows and runs $50 to $100 more per unit than clear double-pane. Triple-pane windows add another $100 to $200 per unit and cut heating costs 8 to 15% in zones 5 and colder. In warm-weather zones, triple-pane rarely pays back within 20 years, so stick with quality double-pane with low-SHGC coatings.
