RetractWise

Retractable Awning Size Calculator

By Retract Wise Editorial TeamUpdated Editorial standards

Choose a projection that covers the depth you want shaded, make the awning at least a foot wider than the area it covers, and then check that the front bar still clears heads at the pitch you need for rain runoff. This calculator does all three checks at once and flags the combinations that fail.

Measured from patio surface to the bracket line
14° is about 3 in of fall per foot
80 in (6 ft 8 in) matches a standard door

Key takeaways

  • Every foot of projection at 14° pitch drops the front bar about 2.9 in. A 12 ft awning drops almost 3 ft.
  • For standard lateral arms, make the width at least 1-2 ft greater than the projection so folded arms do not collide.
  • Low mounting height is the most common sizing constraint, not wall width.
  • Projection sets maximum shade; actual shade at a given hour is usually less.

The geometry behind the numbers

A retractable awning is a straight line hinged at the wall. Its front bar sits projection × sin(pitch) below the bracket. Add the valance and you have the lowest point people walk under.

Front bar drop below the bracket, by projection and pitch (no valance)
Projection10°14°18°22°
8 ft (2.4 m)1 ft 5 in1 ft 11 in2 ft 6 in3 ft 0 in
10 ft (3.0 m)1 ft 9 in2 ft 5 in3 ft 1 in3 ft 9 in
12 ft (3.7 m)2 ft 1 in2 ft 11 in3 ft 8 in4 ft 6 in
13 ft (4.0 m)2 ft 3 in3 ft 2 in4 ft 0 in4 ft 10 in
Worked example: You want 12 ft of projection, the brackets can go at 8 ft 6 in, and you want 80 in of headroom with an 8 in valance. Drop at 14° is 2 ft 11 in, so the valance bottom sits at 8 ft 6 in − 2 ft 11 in − 8 in = 4 ft 11 in. That fails badly. Options: mount at the soffit or roof (at least 10 ft 7 in), cut pitch to about 5° (too flat for rain), or cut projection to about 6 ft at 14°. This is why second-story or soffit mounting is so common on single-story homes with low eaves.
Retract Wise analysis: on single-story houses with 8 ft wall plates, bracket height usually caps practical projection at 9-10 ft at a rain-shedding pitch. Before paying for a 13 ft frame, confirm you can mount high enough to use it. If not, the money is better spent on a wider awning or a drop screen.

Width rules

  • Overhang: add about 6 in each side beyond the area you need covered so afternoon sun at an angle does not clip the edge seats.
  • Arm clearance: two-arm lateral awnings need the width to exceed projection, usually by 1-2 ft. Some makers offer crossed or stacked arms for narrow, deep installs.
  • Brackets and obstacles: brackets must land on structure. Check where your studs, rim joist or rafters are before fixing the final width; see finding structural backing.
  • Very wide spans: above roughly 20-24 ft, expect a third arm or two coupled units.

Choosing a pitch

Most manufacturers allow roughly 5-35° (some to 45° or more on specific brackets). Rain shedding starts to work reliably around 14° and up; below 10° puddles are likely. See awning pitch explained for the full trade-off between headroom, view, rain and late-day shade.

Frequently asked questions

What is a standard retractable awning size?

Common stock widths run 8-20 ft in 1-2 ft steps, with projections of 7-10 ft for mainstream residential models and up to about 13 ft (4 m) for heavy-duty frames. Custom makers build in inch or centimeter increments.

Can the projection be longer than the width?

Not with a standard two-arm layout, because the folded arms would overlap. You need a crossed-arm option, a narrower projection, or a different product such as a pergola-style system with guide rails.

How high should a retractable awning be mounted?

High enough that the valance clears about 80 in at your chosen pitch. For a 10 ft awning at 14° with an 8 in valance, that means brackets at roughly 9 ft 5 in or more.

Should I size to the patio or to the shade I want at a certain time?

Size to the shade you want at the hours you use the space. Run your intended size through the shade calculator for those hours and adjust.

Does a bigger awning need stronger mounting?

Yes. Load on the brackets rises with both width and projection, and projection acts as a lever. Long projections need more brackets and solid structural backing.