How to Measure for an Awning (Patio, Window, Door and RV)

To measure for an awning you need four numbers: the usable mounting width on the wall, the depth (projection) you want the awning to reach, the height of the highest solid mounting point, and the headroom left at the front edge once the awning is pitched for drainage. Width and projection decide what gets shaded. Mounting height and pitch decide whether people can walk under it and whether rain runs off. Most ordering mistakes come from measuring the patio rather than the wall, or from forgetting that a sloped awning ends lower than where it starts.

This guide covers patio, window, door and RV awnings. If you already have your numbers, the awning size planner turns them into a recommended width, projection and pitch, and the shade calculator shows how far the shadow will actually reach on the ground at your latitude and time of day.

Tools and terms before you start

You need a 25 ft tape measure, a 4 ft level, a stud finder, a ladder, and a helper to hold the far end of the tape. A photo of the wall with dimensions written on it is the most useful thing you can send a dealer.

• Width: the overall side-to-side size, usually across the roller tube or cassette. Brands differ on whether end caps and brackets are included, so check the spec sheet.
• Projection: how far the awning extends from the wall, roughly the arm length on a retractable.
• Pitch: the angle below horizontal. Retractables commonly adjust from about 5 to 35 degrees.
• Drop: how much lower the front bar sits than the mounting point.

Other part names (front bar, valance, torsion bar) are defined in the awning glossary.

Step 1: measure the usable mounting width

Measure the wall, not the patio. A 20 ft patio against a 14 ft stretch of clear wall can only take a 14 ft awning on that wall. Run the tape horizontally at bracket height and stop at the first thing a bracket or the roller housing cannot pass: downspouts, light fixtures, cameras, hose bibs, proud window or door trim, shutters, inside corners (end caps and folding arms need side clearance), and changes in wall material. Never mount over a gas meter or a vent termination.

For the target width, a common rule is the seating or dining area plus about 1 to 2 ft per side, because shade shifts sideways as the sun moves. Many lateral-arm brands offer single units up to about 20 ft wide, and wider runs use coupled units. Lateral arms fold side by side inside the width, so most brands require the width to be at least equal to the projection. A 10 ft wide, 13 ft deep awning usually is not possible without a special configuration.

Step 2: measure the projection you need

Measure from the wall to the edge of the area you want covered. Typical lateral-arm projections run from 8 to 13 ft, with some brands offering 14 to 15 ft. Longer arms put more load on the wall and catch more wind, so bigger is not automatically better.

Two corrections matter. First, slope shortens coverage: a 10 ft arm at 14 degrees covers about 9.7 ft horizontally (10 x cos 14). Second, shade is not the same as coverage. When the sun is high the shadow falls close to the wall, and late afternoon sun on a west wall can push the shadow past the front bar or off the patio entirely. Run your latitude, wall orientation and the hours you sit outside through the shade calculator. The full geometry, with a table of drop at every common pitch, is in awning projection and pitch.

Step 3: find the mounting height

Measure from the patio surface (where people will stand) up to the highest point where brackets can go into solid structure. On a single-story house with 8 ft ceilings, that is usually somewhere between about 8 and 10 ft, often over the door header or along the rim joist on a raised floor. Record three heights:

• Soffit or eave underside: the ceiling for a wall mount, minus the vertical space the manufacturer says its brackets and housing need.
• Top of the tallest door or window: brackets usually sit above this so folded arms do not block it.
• Solid framing band: header, rim joist, top plates, or a masonry course you can anchor into.

If there is no usable wall height, the awning may need soffit or roof mount brackets. On brick, stucco or siding over unknown framing, read mounting awnings on brick, siding and stucco first, because anchor location often decides the height.

Step 4: check head clearance at the front bar

This is the step most people skip. The front bar ends lower than the brackets by the drop, and a valance hangs below that:

Front bar height = mounting height minus (projection x sin pitch) minus valance depth.

Aim for at least 80 inches (6 ft 8 in, the height of a standard door) under the lowest point, and 84 inches or more on walkways or for tall households. If the result is too low, mount higher, shorten the projection, or flatten the pitch (accepting slower drainage).

Measuring for a patio awning (retractable or fixed)

Retractable lateral-arm awnings need everything above. Fixed patio awnings on aluminum or steel frames usually have front posts, so the projection is set by where the posts land and headroom is checked at the front beam.

• Confirm every bracket position can hit framing or masonry along the full width.
• Check outward-swinging casement windows and storm doors against the front bar and valance.
• Note where power could go for a motor; an electrician typically charges $200 to $800 for a dedicated outlet or hardwired circuit.
• Note ground slope: a patio that rises away from the house loses headroom at the front.

To compare styles first, see patio awnings.

Measuring for a window awning

Window awnings are sized to the outside edge of the trim, not the glass.

1. Width. Measure the outside of the trim and add 3 to 6 inches per side. Go wider on east and west windows, where sun arrives at an angle.
2. Projection. On south-facing windows, roughly one half to two thirds of the window height blocks high summer sun while admitting low winter sun. A 48 in tall window takes about a 24 to 32 in projection. East and west windows need deeper projection or side panels.
3. Mounting height. Window awnings typically mount several inches above the top trim so the valance does not cut into the view and the frame anchors into the header. Measure up to the soffit or next obstruction.
4. Drop. Decide how far down the window the awning should come: more drop blocks more sun and more view.

Measure every window separately; trim and header heights vary on older houses. More in the window awnings guide.

Measuring for a door awning or canopy

Measure the outside of the door trim and add about 6 to 12 inches per side so angled rain still misses the threshold. A projection of about 3 to 4 ft covers one person at the door; 4 to 5 ft also covers a small landing. Measure headroom from the top step or landing, not the walkway below, subtract the canopy's drop, and keep at least 80 inches under the lowest edge, more if a storm door swings outward. Decide whether a wall light or doorbell camera moves or the canopy goes above it.

Measuring an RV awning

For most RV patio awnings, the awning size is the distance from the center of one arm to the center of the other, rounded to the nearest foot. The fabric is a few inches narrower than that, so do not order replacement fabric by measuring the old fabric edge to edge.

• Measure arm center to center with the awning closed.
• Note the brand and model (for example Dometic, Lippert/Solera or Carefree of Colorado).
• Measure projection extended, from the coach side to the roller tube.
• Note obstructions along the rail: entry door, slide-out toppers, lights.

The RV awnings guide covers types, sizing and replacement options.

Measurement worksheet summary

Measure yourself or have the installer measure?

Measure yourself if you are buying a direct-to-consumer retractable or a stock window awning for a simple wood-framed wall and can confirm framing locations. Measure twice and photograph the wall, because your numbers decide what you order.

Have a dealer or installer measure if the wall is masonry or stucco, the mount is above a single story, you need soffit or roof brackets, the awning is custom (fixed frames, cassettes, coupled units), or you want the installer responsible for the fit. Most dealers include a site measure in the quote. Exposed sites (open water, hilltops, upper floors) call for conservative projections; see awning wind ratings. Before ordering, check awning permits and HOA rules, and if you are installing it yourself, continue with DIY awning installation.

For the trade-off between going wider and going deeper, see awning width vs projection.

Frequently asked questions

How high should a patio awning be mounted?

High enough that the front bar, after the awning drops at its working pitch, still sits at least 80 inches above the patio. On most single-story homes that means brackets around 8 to 10 ft high. Calculate the drop as projection times the sine of the pitch, add any valance, and confirm the result leaves headroom. If the wall is too short, consider soffit or roof brackets.

Should an awning be wider than the window or door?

Yes. Window awnings typically extend 3 to 6 inches beyond each side of the trim, and door canopies about 6 to 12 inches per side. The extra width blocks sun and rain arriving at an angle. East and west windows benefit from more width or side panels because the sun reaches them at a low angle in the morning and afternoon.

Can a retractable awning project farther than it is wide?

Usually not. Lateral arms fold side by side inside the awning's width, so most manufacturers require the width to be equal to or greater than the projection, sometimes with a margin. Some offer crossed-arm or special configurations for narrow, deep spaces. Check the brand's size chart before planning a narrow, deep awning.

How do I measure an RV awning for replacement fabric?

Measure from the center of one awning arm to the center of the other with the awning closed, and round to the nearest foot. That figure is the awning size used to order fabric for most RV awnings. The fabric itself is a few inches narrower, so measuring the old fabric edge to edge will usually lead you to order the wrong size.

Sources and further reading

• U.S. Department of Energy, Energy Saver: Energy Efficient Window Attachments
• International Code Council, International Residential Code (IRC), provisions on door and egress heights
• Professional Awning Manufacturers Association (PAMA), consumer resources on awning selection
• Advanced Textiles Association (formerly IFAI), Specialty Fabrics Review articles on awning design
• Manufacturer measuring guides and spec sheets for lateral-arm awnings and RV awnings (for example Dometic and Carefree of Colorado)