Standard window sizes depend on the style. Double hung windows commonly run 24 to 48 inches wide and 36 to 72 inches high. Sliding windows are wider and shorter, at about 36 to 84 inches wide and 24 to 60 inches high. There's no single average window size, so measure your opening before you order.

The Window Depot carries vinyl and aluminum windows for homeowners and contractors at its stores in Tucson, Phoenix, Chandler, Surprise, El Paso, Albuquerque and National City. This guide covers common window dimensions by style and explains how to measure for replacement windows.

What Are Standard Window Sizes?

Standard window sizes are dimensions manufacturers commonly produce to fit typical residential openings. Because they're common sizes, they're often easier to find and quicker to get than custom windows.

"Standard" doesn't mean every home uses the same sizes, though. Here are common size ranges by window style:

Use these ranges as a starting point. They don't guarantee that a particular size will fit your opening. For more help choosing a size for your home, see our guide to finding the right window size. 

What Are the Standard Sizes for Each Window Style?

Each style has its own typical proportions because of the way it opens.

Standard Double Hung Window Sizes

Double hung windows are usually taller than they are wide because the sashes slide up and down. Common sizes range from 24 to 48 inches wide and 36 to 72 inches high. They're a popular choice for bedrooms and living rooms.

Standard Sliding Window Sizes

Sliding windows open side to side, so they tend to be wider than they are tall. Common sizes range from 36 to 84 inches wide and 24 to 60 inches high. They work well where you want a broad view without a tall window.

Standard Picture Window Sizes

Picture windows don't open, so they come in a much wider range of sizes, from 24 to 96 inches wide and 12 to 96 inches high. They're often used where natural light and views matter most.

Standard Casement Window Sizes

Casement windows are hinged on the side and crank outward. Common sizes run 14 to 35.5 inches wide and 29.5 to 77.5 inches high. Their tall, narrow shape is good for catching a breeze.

Standard Awning Window Sizes

Awning windows are hinged at the top and open outward from the bottom, which helps keep light rain out when they're open. Common sizes range from 24 to 46 inches wide.

What Is the Average Size of a Window?

There's no single average window size, because each style has different proportions. A double hung window is usually taller and narrower than a slider, and a picture window can be much larger than either. A more useful approach is to identify your window style and then compare its common size range with your actual opening.

What's the Difference Between Nominal and Actual Window Size?

A nominal size is the name a manufacturer uses to identify a window, such as "36 x 60." The actual unit dimensions are often slightly different, so the window will fit the opening it was designed for.

Two windows with the same nominal size can also measure differently, because manufacturers use different frame profiles and designs. Always compare the manufacturer's actual unit dimensions with your measured opening rather than going by the size in the product name.

How Do You Measure for a Replacement Window?

Measure the opening at several points, because older openings are rarely perfectly square.

1. Measure the width at the top, middle and bottom of the opening.
2. Measure the height on the left side, in the center and on the right side.
3. Write down the smallest width and the smallest height.
4. Measure both diagonals. If they differ significantly, the opening may be out of square.
5. Check the frame, sill and surrounding wall for damage, warping or signs of moisture.
6. Compare your measurements with the manufacturer's actual dimensions and measuring instructions.

If the opening is damaged or badly out of square, have a qualified professional look at it before you order.

For contractors: Measure every opening on its own, even if the windows look identical. Settling and past renovations can leave matching windows a little different in size. Labeling each measurement by room and wall makes ordering much easier.

Can You Change the Size of a Window Opening?

Sometimes, but it makes the project bigger. A larger window may require new framing, a header, and repairs to the interior and exterior walls. A smaller window means filling part of the opening. Keeping the existing opening size is usually the simplest way to replace a window.

When Does a Custom Size Window Make Sense?

A custom size is worth considering when your opening doesn't line up with any common size. That's often the case in older homes or homes with unusual architectural features. Custom windows can cost more and take longer to arrive than standard sizes.

Does Window Size Affect Energy Efficiency?

Size plays a role, but it isn't the whole story. A bigger window has more glass exposed to the sun, and that matters most on west- and south-facing walls in Tucson, Phoenix, El Paso and Albuquerque. Glass type, frame material and NFRC ratings such as U-Factor and Solar Heat Gain Coefficient (SHGC) usually matter more than the dimensions.

If you're adding glass on a sunny wall, a window with a lower SHGC can help keep heat out. Our guide on energy efficient windows for hot climates explains what to look for.

What Size Window Do You Need for a Bedroom?

There's no single best size for a bedroom window. Bedrooms often have to meet egress (emergency escape) requirements in local building codes, which set a minimum opening size and a maximum sill height. Check the code where you live before you change a bedroom window's size or style.

Frequently Asked Questions About Standard Window Sizes

What is the most common window size?

There's no single most common size across all homes. Double hung windows commonly fall between 24 and 48 inches wide, while sliding windows usually run 36 to 84 inches wide.

Are standard window sizes the same for every manufacturer?

No. Each manufacturer has its own sizing and actual unit dimensions. Always compare the specific product's dimensions with your measured opening.

How do I know what size replacement window I need?

Measure the width in three places and the height in three places, and use the smallest of each. Then compare those numbers with the manufacturer's actual unit size.

Can I put a standard size window in an older home?

Often, yes, as long as the window's actual dimensions work with the existing opening. If the opening is an unusual size or badly out of square, a custom window may fit better.

Where can I buy standard size windows in Tucson or Phoenix?

The Window Depot carries vinyl and aluminum windows, including Milgard and SI Windows, at stores in Tucson, Phoenix, Chandler, Surprise, El Paso, Albuquerque and National City.

Find the Right Size Window at The Window Depot

Bring your measurements to The Window Depot in Tucson, Phoenix, Chandler, Surprise, El Paso, Albuquerque or National City, and the staff can help you compare sizes and styles. Browse vinyl windows online, or find your nearest store.