How to Measure RV Skylight? Size and Measuring Tips is reader supported. When you buy through links on our site, we may earn an affiliate commission.

An RV does not have as many windows as in a home. Its interior space also remains cramped due to placing too many items in a small setting. Skylights can breathe life into the dark, cramped motorhome interior by washing it with natural sunlight.

You can save on daytime lighting bills besides enjoying a lifted-up mood while bathing in the warmth of natural light. But many RVers don’t know how to measure RV skylight to install a new one or replace the old unit. Learning about the measurements will save you from many hassles down the road.

how to measure rv skylight
Photo: Virrage Images / ShutterStock

The Average Size of RV Skylights

If the motorhome does not have a skylight, you will have to cut a hole in the roof. So, it’s essential for you to know the exact dimensions and learn how to measure RV skylight. A good DIYer should always measure twice and cut once. Remember that cutting a wrong-sized hole on the roof may cost hundreds of dollars in repairs.

Learning the dimensions is necessary for replacing old skylights too. Otherwise, you will be just wasting time and money in returning the wrong products.

Standard Skylight Dimensions

There are no definite standard dimensions for RV skylights. There are fixed dome, ventilating, and few more skylight types for travel trailers, and the dimensions of these products depend on their manufacturers. That is to say, they are available in various sizes, so RVers can choose one according to the size of your trailer.

a. Fixed-dome

Fixed-dome is the most popular skylight to be found in most travel trailers. If an RV has a factory-built skylight, it will most probably be a fixed-dome model. If you want to install one, you need to learn about the particular model’s outer and opening dimensions.

For example, if a unit’s outer dimensions are 33 x 25 ¼ x 2 inches, its opening dimensions are likely to be 30 x 22 inches. Also, a dome skylight may have 28 x 22 x 6 inches of dome dimensions with 34 x 28 inches of outer dimensions.

measuring rv skylight
Measuring a fixed-dome skylight. Photo: Wander Inn

b. Flat tempered glass

A flat tempered glass skylight could be a good choice for any type of travel trailers — big or small. A standard unit could be anywhere between 16 and 96 inches in length and 14 and 72 inches in width.

c. Tubular

On the other hand, if you decide to install a tubular skylight, you will need to make room for 14 ½ inches of opening because most of them have this width. However, they are available at up to 22 inches in diameter. Using tubular skylights for an RV is rare because they are normally installed between two rafters of a house roof.

When you are cutting a hole on the trailer roof, the actual height and width of the skylight don’t matter much. What you need to pay attention to are the opening dimensions. Depending on that, you have to measure the exact size of the opening hole.

Glass Thickness

Apart from the metal frame, the rest of the skylight is made of glass for easy travel of lights. Well, you don’t need to measure the glass thickness but it indicates how well it can pass on the illumination.

Skylight glass thickness can be between 3.2 mm and 6.35 mm. However, dual-glass panels can have a thickness of up to 25 mm or 1 inch. Normally, larger skylights have thicker glass but thickness is not proportional to strength. So, your skylight having thin glass does not mean that it will be vulnerable to external pressure.

Skylight Weight

The size of the skylight affects its weight. Well, it’s quite normal that the bigger the skylight is, the heavier it will be. The materials used in making the product also affect this parameter a lot. For example, a skylight made of aluminum will be lighter than the one made of stainless steel.

It could be troublesome for one person to install a large skylight. Some bigger ones can easily be over 150 pounds, which is impossible for anyone to handle without any help.


If you have a tiny trailer or want to install the skylight in an oddly-shaped spot on the roof, it will be better to go with customized size. Many skylight manufacturers take orders for customized products. All you have to do is to measure the area where you want to install the skylight and send the dimensions to the company.

Custom skylights will require a longer shipping time. You may have to wait for a month to get the delivery. If you learn how to measure RV skylight, you can easily go for the customized option.

How to Measure RV Skylight? Follow These Tips

So, we’ve learned all the details about the dimensions of RV skylights. It’ll now become easier for you to measure the skylight and its opening on the trailer roof. For how to measure RV skylight, you still need to follow these tips to finish the measuring task perfectly.

1. Select a suitable spot

Choosing the right spot for the skylight is highly important. You cannot just pick a random spot because an RV roof is full of electrical wiring, just like a residential home. Slicing up one of the wires accidentally while cutting a hole on the roof will not only leave you without electricity but also an expensive repair task.

rv skylight measuring tips
Installation does not require much skill. (Credit: RVgeeks / YouTube)

2. Choose the skylight

You should pick up the RV skylight according to the available space in the installation spot. In case if you are replacing an old skylight, take it off by loosening the screws. Then, measure its height, width, and depth along with measuring the dimensions of the opening on the roof.

Purchase a new skylight that matches these dimensions. If you want to install the light in an odd space, a custom-made one will be the right choice. However, a ready-made product will always be cheaper than a custom-made one.

3. Cut the opening

Choose the thinnest part of the roof that does not have any electrical or other wirings. If you are not confident enough to cut through the roof, ask for the help of an expert mechanic. When the opening is ready, install the skylight.

About Peter Wade

Peter Wade is a co-ordinator and writer at His hobbies are coffee, RV camping and photography. He now enjoys exploring the U.S. by RV with his two dogs. After obtaining a MA degree in Public Relations and Journalism, he had 8 years of experience working for the R&D Department of Outdoorsy. Peter provides a unique look and insightful knowledge about the RV lifestyle, and fills his blog with everything from RV camping guides to reviews about necessary RV accessories. If you are an RV enthusiast and want to get the most-updated trends of the RV industry, Peter’s articles are the must-visit contents.

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