Standard window measurements in Canadian homes range from 24 inches wide by 24 inches tall for small casements and basement hoppers, up to 72 inches wide by 60 inches tall for large picture or bay windows. Most residential windows fall in the 24 to 48 inch width range and 36 to 60 inch height range, but “standard” sizes vary by window style and manufacturer.
- Rough opening measurements (the framed hole in the wall) are always larger than the window unit itself: allow about ½ inch per side for shimming and insulation.
- Window sizes are typically given as width × height in inches in Canada (for example, 36×48 means 36 inches wide by 48 inches tall).
- Casement, double-hung, and slider windows each have different standard size ranges because of how they operate and how large they can be while remaining functional.
- If your opening is a non-standard size, most vinyl window manufacturers, including TotalSeal, make windows to custom dimensions at no significant premium over standard sizing.
- Always measure the rough opening in three places (top, middle, and bottom for width; left, centre, and right for height) and use the smallest measurement to order.
What “Standard Size” Means for Windows
Unlike doors, which have closely observed standard dimensions (80 inches tall being almost universal in Canadian residential construction), windows don’t follow a single rigid standard. Each window style has its own common size range, and different manufacturers use slightly different module sizes. What “standard” really means in practice is that a particular window size is stocked or produced regularly, which speeds up lead times and sometimes lowers costs.
Non-standard or custom sizes are very common in replacement work, where the existing rough opening determines the window size. Most vinyl window manufacturers work to custom dimensions without a significant cost premium, particularly for smaller projects.
Standard Sizes by Window Type
Casement Windows
Casement windows are hinged on one side and open outward with a crank. Their operating mechanism limits maximum width: a sash wider than about 30 to 36 inches becomes difficult to crank and may flex under wind pressure.
| Width (inches) | Height range (inches) | Common use |
| 18 to 24 | 24 to 60 | Narrow openings, beside larger fixed units |
| 24 to 30 | 24 to 72 | Most common single casement size |
| 30 to 36 | 36 to 72 | Wide single casement; near maximum practical width |
Casement windows are popular in GTA homes for their tight seal when closed (the sash compresses against the frame) and their good ventilation when open.
Double-Hung Windows
Double-hung windows have two sliding sashes, both of which open. They’re wider in standard sizing than casements because neither sash needs to extend beyond the frame.
| Width (inches) | Height range (inches) | Common use |
| 24 to 36 | 36 to 60 | Most common double-hung size |
| 36 to 48 | 36 to 72 | Larger openings, living rooms, bedrooms |
| 48 to 60 | 48 to 72 | Wide openings; often seen in older GTA homes |
Slider Windows
Slider windows open horizontally. Common configurations are 2-light (one fixed, one sliding) and 3-light (fixed-sliding-fixed). Width is typically larger than height.
| Width (inches) | Height range (inches) | Common use |
| 36 to 48 | 24 to 36 | Small utility sliders (garage, laundry) |
| 48 to 60 | 30 to 48 | Standard living area sliders |
| 60 to 72 | 36 to 60 | Wide sliders in modern builds |
Slider windows are common in GTA bungalows and ranch-style homes where horizontal openings suit the architecture.
Awning Windows
Awning windows are hinged at the top and open outward at the bottom. They’re often used in combination with fixed picture windows below and above.
| Width (inches) | Height range (inches) | Common use |
| 24 to 36 | 12 to 24 | Clerestory or high-wall positions |
| 36 to 48 | 18 to 30 | Most common awning size |
| 48 to 60 | 18 to 36 | Wide awnings; common above kitchen sinks |
Picture / Fixed Windows
Fixed windows have no operating sash. They can be made in almost any size because there’s no mechanism to limit the dimensions. Very large units may require structural considerations in the rough framing.
| Width (inches) | Height range (inches) | Common use |
| 24 to 48 | 24 to 60 | Standard fixed units for living areas |
| 48 to 72 | 36 to 72 | Large picture windows |
| 72 to 96+ | 48 to 96 | Feature windows; custom framing required |
Fixed and picture windows deliver the best thermal performance per dollar because there’s no hardware or operable sash to compromise the seal.
Basement Hopper Windows
Basement hopper windows are hinged at the bottom and tilt inward at the top. They must meet egress requirements in Ontario if the room is used as a bedroom.
| Width (inches) | Height range (inches) | Notes |
| 24 to 36 | 12 to 18 | Standard basement utility windows |
| 30 to 36 | 18 to 24 | Common in older GTA basements |
| 36 to 48 | 24 to 30 | Larger hopper; may meet egress |
Ontario’s Building Code requires basement bedroom windows to have a minimum unobstructed opening of 0.35 m² and a minimum opening height and width of 380 mm each.
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Standard Sizes in Millimetres (SI Units)
Canadian building plans and codes use millimetres. Here’s a quick conversion for common sizes.
| Common description | Width (mm) | Height (mm) |
| 24×36 | 610 | 915 |
| 30×48 | 762 | 1219 |
| 36×48 | 915 | 1219 |
| 36×60 | 915 | 1524 |
| 48×60 | 1219 | 1524 |
| 60×60 | 1524 | 1524 |
| 72×48 | 1829 | 1219 |
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How to Measure Your Window for Replacement
Measuring correctly is the most important step in ordering a replacement window. A window ordered even 5 mm too wide will not fit into the rough opening; one ordered too narrow will leave excessive gaps that are hard to insulate and seal properly.
Step 1: Measure the Rough Opening
The rough opening is the framed hole in the wall structure, before any interior or exterior casing is applied. To access it, you’ll need to remove the interior window stop beads or trim on at least one side, or measure from the visible edge of the existing window frame to the wall stud.
Measure width in three places: across the top, the middle, and the bottom. Measure height in three places: left side, centre, and right side. Record all six measurements and use the smallest width and the smallest height to determine your maximum window unit size.
Step 2: Subtract for Shimming Gap
Subtract about 12 to 20 mm (½ to ¾ inch) from each dimension to leave room for shims and low-expansion foam insulation on all four sides. This is the net opening size you order to.
| If rough opening is | Order window unit at |
| 915 mm wide | 890 to 895 mm wide |
| 1219 mm wide | 1194 to 1200 mm wide |
| 1524 wide | 1499 to 1505 mm wide |
Step 3: Confirm Frame Depth
For an insert replacement (where the new window fits inside the existing frame), measure the depth of the existing frame from the interior stop to the exterior stop. The new window must fit within that depth.
Step 4: Note the Rough Opening Square
Check whether the rough opening is square by measuring both diagonals. If they differ by more than 5 mm, the opening is out of square and you’ll need to shim one corner more than the other to bring the new frame into alignment.
“The most common measuring mistake is ordering to the existing window’s outer frame dimension rather than the rough opening,” says a lead installation manager at TotalSeal. “The rough opening is always the number you need. If you can’t access it directly, let an installer come and measure before you order anything.”
What If My Window Is a Non-Standard Size?
Custom sizing is the norm in replacement work, not the exception. Older GTA homes from the 1950s through 1980s were built with rough openings that don’t match any current standard module. A good vinyl window manufacturer can produce windows to any practical custom dimension without a significant cost premium over a catalogue size.
“We build to custom dimensions every day,” says a senior product engineer at TotalSeal. “Our automated manufacturing line handles non-standard sizes without the long lead times you’d expect from a custom order. For most sizes, it’s the same lead time as a catalogue item.”
The main limitation is physics: very wide sashes in operating styles (casement, awning, double-hung) become difficult to operate and may flex under wind load. A wide opening is often better served by a combination of a fixed centre panel with operating sidelites rather than a single very wide sash.
Standard Rough Opening Dimensions by Style
As a quick reference guide for new construction or major renovation planning:
| Window style | Typical rough opening width (mm) | Typical rough opening height (mm) |
| Single casement | 610 to 915 | 610 to 1830 |
| Double casement | 915 to 1525 | 610 to 1830 |
| Double-hung (single) | 610 to 1220 | 915 to 1830 |
| Slider (2-light) | 915 to 1830 | 610 to 1220 |
| Awning | 610 to 1525 | 305 to 915 |
| Picture / fixed | 610 to 2440 | 610 to 2440 |
| Basement hopper | 610 to 1220 | 305 to 760 |
Frequently Asked Questions
What is the most common window size in Canadian homes?
The most common residential window width in Canada is 30 to 36 inches (762 to 915 mm), with heights typically 36 to 48 inches (915 to 1219 mm). These dimensions suit standard wall framing on 2×4 or 2×6 studs with normal ceiling heights.
Are window measurements given as width x height or height x width?
In the window industry in Canada, sizes are quoted as width first, then height. A “3040” window is 30 inches wide by 40 inches tall, and a “36×48” window is 36 inches wide by 48 inches tall.
Do I measure the window frame or the glass to order a replacement?
Neither alone. You measure the rough opening (the framed hole in the wall) and subtract a shimming allowance on each side. The window unit must fit inside the rough opening with room for shims and insulation.
What is the minimum window size for a bedroom egress in Ontario?
Ontario’s Building Code requires bedroom windows to have an unobstructed opening area of at least 0.35 m², with a minimum opening height and minimum opening width of 380 mm each. Basement bedroom windows must also allow a person to escape in an emergency.
Can I get a window in a non-standard size?
Yes. Most vinyl window manufacturers, including TotalSeal, produce custom sizes to your rough opening dimensions. Custom sizing rarely adds significant cost for standard configurations.
How much smaller should the window be than the rough opening?
The window unit should be 12 to 20 mm smaller than the rough opening in both width and height (6 to 10 mm per side), leaving room for shims and low-expansion foam insulation on all four sides.
Ready to Order?
If you’re not confident about your measurements or want a professional to confirm before ordering, TotalSeal offers a free in-home measurement and quote. Our installers measure to the rough opening, confirm the frame depth, check for square, and handle the order from there.
