How Much Shade Does an Awning Provide? Shade Depth, Area and Quality Explained
Quick answer
At summer solar noon a 10 ft awning on a south wall with its front bar at 7.5 ft shades roughly 7 to 9 ft of ground across the US, but less by the September equinox and much less on west walls in late afternoon. Shade depth equals horizontal reach minus front bar height divided by the tangent of the sun's profile angle, so projection, front bar height, wall direction and time of day all matter.
An awning shades less ground than it covers, and how much less depends on the sun. On a south-facing wall at solar noon in June, a 10 ft (3.05 m) awning with its front bar 7.5 ft (2.29 m) above the patio shades about 7 to 9 ft of ground in US cities between 25 and 48 degrees north. By the September 21 equinox the same awning shades about 6 ft in Miami but under 2 ft in Seattle. On a west wall in August the shaded strip shrinks from about 8 ft at 1 pm to nothing by roughly 4 pm solar time, because the low sun slides straight under the front bar.
This guide explains the geometry behind those numbers, what changes them, and how to size an awning for the shade you actually want. All figures come from the same standard solar formulas used on our awning shade data page, and you can run your own location in the shade calculator.
Footprint is not shade
The footprint of an awning is the rectangle of ground directly beneath it: width times horizontal reach. The shadow is that rectangle projected along the sun's rays, so it is pushed away from the sun. Two things happen:
- The shadow moves toward the wall. Because the sun is in front of the wall, the shadow of the front bar falls somewhere under the awning, not at its outer edge. The strip between the front bar and that shadow line is sunlit even though it is "under" the awning.
- The shadow slides sideways. Unless the sun is square to the wall, the whole shaded patch shifts along the wall, away from the sun. A table centered under the awning can end up half in the sun even when the total shaded area is large.
The shade depth formula
For a flat patio and a straight wall, the depth of shade measured out from the wall is:
- Shade depth = horizontal reach minus (front edge height / tan(profile angle))
- tan(profile angle) = tan(sun altitude) / cos(sun azimuth minus wall azimuth)
The profile angle is the sun's height seen in a vertical slice straight out from the wall. It equals the altitude when the sun is square to the wall and is steeper when the sun is off to one side. The "front edge height" is the lowest edge that blocks light: the bottom of the valance or a drop shade if you have one, not the bracket height.
Horizontal reach is projection x cos(pitch) (see the projection and pitch guide). A result of zero or less means the ground in front of the wall is in sun.
Worked example
A 12 ft wide by 10 ft awning on a south wall at 40 degrees north (about the latitude of Denver, New York or Philadelphia), front bar at 7.5 ft, August 1 at solar noon. The sun is about 67.9 degrees high and due south, so the profile angle is also 67.9 degrees and tan(67.9) is about 2.46.
Shadow offset = 7.5 / 2.46 = 3.0 ft. Shade depth = 10 minus 3.0 = 7.0 ft. Shaded area = 12 x 7.0 = 84 sq ft, or 70% of the 120 sq ft footprint.
Same awning on September 21: the sun is about 49.8 degrees high, tan is 1.18, offset is 6.3 ft, and shade depth falls to 3.7 ft (44 sq ft, 37% of the footprint). Lowering the front bar to 6.5 ft by adding pitch raises that to 4.5 ft; a 12 ft projection at the original height gives 5.7 ft.
What changes the amount of shade
| Factor | Effect on shade | Rule of thumb |
|---|---|---|
| Projection | Adds shade one for one once the shadow is past the wall | Each extra foot of reach adds about a foot of shade depth |
| Front edge height | Lower edge pushes the shadow outward | Each foot lower adds 1 / tan(profile angle) ft: about 0.3 ft at June noon, 0.85 ft at the equinox, 1 ft or more in late afternoon |
| Valance or drop shade | Lowers the effective front edge | The most effective fix for low sun; see west walls below |
| Wall direction | Controls when the sun is square to the awning | South: steady; east and west: strong in one half of the day only |
| Latitude and season | Lower sun means a shallower shadow | Northern cities lose shade fastest after midsummer |
| Side panels | Block sun from the side | Help most on east, west and angled walls |
Front edge height is the factor most people underestimate. At midsummer noon lowering the front bar barely matters, but in September or mid-afternoon each foot of drop is worth close to a foot of shade, which makes a pitch change or deeper valance the cheapest upgrade for an existing awning.
Shade depth by city and season
These figures are for the reference awning (10 ft reach, front bar 7.5 ft, flat ground) on a wall facing due south, at solar noon. They are drawn from the full tables on the shade research page.
| City (latitude) | Jun 21 | Aug 1 | Sep 21 |
|---|---|---|---|
| Miami (25.8 N) | 9.7 ft | 9.0 ft | 6.3 ft |
| Phoenix (33.4 N) | 8.7 ft | 7.9 ft | 5.0 ft |
| Washington, DC (38.9 N) | 7.9 ft | 7.1 ft | 3.9 ft |
| Chicago (41.9 N) | 7.5 ft | 6.7 ft | 3.2 ft |
| Minneapolis (45.0 N) | 7.0 ft | 6.2 ft | 2.4 ft |
| Seattle (47.6 N) | 6.6 ft | 5.7 ft | 1.7 ft |
In midsummer every city gets most of its footprint shaded. Between August and the equinox, northern cities lose more than half their noon shade while southern cities keep most of it. North of about 40 degrees, if you use the patio into September, plan for the September number.
Time of day and wall direction
The noon figures above are the best case for a south wall. Through the day, the picture depends on which way the wall faces:
- South wall: shade depth holds up well all day in summer. At 40 degrees north on August 1 it is about 7.3 ft at 10 am and 2 pm and about 7.9 ft at 3 pm, because the sun swings to the side and the profile angle steepens. At the equinox, a south wall's shade depth stays almost constant all day (about 3.7 ft at 40 degrees north from 10 am to 4 pm).
- West wall: the awning shades about 8 ft at 1 pm solar time, about 5.7 ft at 2 pm, about 3 ft at 3 pm and essentially nothing by 4 pm on August 1, in every city from Miami to Seattle. More projection barely helps; a drop shade does.
- East wall: the mirror image: no useful ground shade before about 9 am solar time, then rapidly improving toward noon.
- North wall: the building shades the patio most of the day; the awning matters mainly for rain.
The full breakdown, including angled walls and what to buy for each, is in our guide to awnings by patio orientation.
The sideways shift most people miss
The shadow of the front bar is displaced away from the sun by front edge height / tan(altitude). Part of that displacement is toward the wall (which sets shade depth) and part is along the wall.
Worked example
Same 12 x 10 ft south-wall awning at 40 degrees north, August 1, 3 pm solar time. The sun is 45.5 degrees high at azimuth 253.7 degrees (73.7 degrees west of the wall's facing direction). Total shadow offset = 7.5 / tan(45.5) = 7.37 ft.
Toward the wall: 7.37 x cos(73.7) = 2.1 ft, so shade depth is 10 minus 2.1 = 7.9 ft. Along the wall: 7.37 x sin(73.7) = 7.1 ft east. The shaded patch is now about 95 sq ft, but only about (12 minus 7.1) x 7.9 = 39 sq ft of it lies under the awning. A table at the west end of the awning is in full sun.
Practical consequences: on a south wall, put afternoon seating toward the east end of the awning (the end away from the afternoon sun), make the awning wider than the space you need, or add a side panel on the sunny end. The shade calculator reports this sideways shift for any time and date.
How good is the shade underneath?
Geometry decides where the shadow lands; the fabric decides how much light, UV and heat get through.
- Light and UV. Tightly woven acrylic and coated fabrics block most direct UV; mesh lets more through by design. Scattered sky UV and reflection from pale paving still reach you, so the Skin Cancer Foundation treats shade as one layer of protection. See UV protection and awnings.
- Heat. Fabric absorbs part of the sun's energy and re-radiates some downward; dark colors run warmer underneath. See awning colors and heat.
- Windows. When the shadow covers glass, the cooling benefit is large: the U.S. Department of Energy, Energy Saver, states that awnings can reduce solar heat gain in summer by up to 65% on south-facing windows and up to 77% on west-facing windows. Our awning energy savings guide works through what that means for a cooling bill.
How to size an awning for the shade you want
- Define the target. Measure the seating area (a 6 ft table with chairs needs about 10 x 10 ft) and the hours and months you use it.
- Find the sun position. Use the sun angle guide or the shade calculator. Convert clock time to solar time: with daylight saving, solar noon in the continental US usually falls between about 12:30 and 2:00 pm.
- Solve for reach and front edge height. Required reach = target shade depth + front edge height / tan(profile angle). Check the front bar still clears about 80 inches for walking.
- Check the limits. Lateral-arm awnings commonly project 8 to 13 ft. If the math asks for more, a valance, drop shade or side panel is usually the better answer. The awning size planner and awning sizing guide handle width and clearance.
Pro tip: Before buying, stand on the patio at the hour you care about and measure the length of a 7.5 ft pole's shadow (or any object of known height). Shadow length / object height = 1 / tan(sun altitude). That one measurement tells you how far the front bar's shadow will fall at that time of year.
Who can rely on an awning for shade, and who needs more
- Awnings alone work well for south-facing patios at any latitude in midsummer, for south and southeast walls in warm southern climates through the season, and for east walls when you use the patio from late morning on.
- Awnings need help on west walls used in the late afternoon, on north-latitude patios used in September, and wherever the seating area is wider or deeper than the awning. Add a drop shade, side panel or a solar screen.
- Consider something else if you need shade far from any wall: a freestanding awning or a pergola with a canopy puts the shade where the seating is.
Frequently asked questions
How much shade does a 10 ft awning give?
On a south wall at summer solar noon, with the front bar at 7.5 ft, a 10 ft awning shades about 7 to 9 ft of ground depending on latitude: about 9.7 ft in Miami and 6.6 ft in Seattle on June 21. By the September equinox that drops to roughly 6 ft in Miami and under 2 ft in Seattle. West walls lose almost all ground shade by late afternoon.
Why is the area under my awning sunny in the afternoon?
The sun is lower and off to one side, so the shadow of the front bar falls back toward the wall and slides along it, away from the sun. On a west wall the sun shines straight under the front bar after about 3 to 4 pm solar time. A drop shade from the front bar or a side panel blocks that low sun far better than extra projection.
Does a lower front bar give more shade?
Yes, and the effect grows as the sun gets lower. Each foot of lower front edge adds about 1 divided by the tangent of the sun's profile angle in shade depth: only about 0.3 ft at June noon, but about 0.85 ft at the equinox and a foot or more in late afternoon. Keep at least about 80 inches of head clearance where people walk.
What is solar noon and why does it matter?
Solar noon is when the sun is highest and due south. Shade calculations use solar time, which differs from clock time because of daylight saving and your position within the time zone. In most of the continental US, solar noon in summer falls between about 12:30 and 2:00 pm on the clock, so "3 pm solar" may be after 4 pm on your watch.
Sources and further reading
- U.S. Department of Energy, Energy Saver: Energy Efficient Window Attachments
- NOAA Global Monitoring Laboratory: NOAA Solar Calculator
- Duffie, J. A. and Beckman, W. A.: Solar Engineering of Thermal Processes (Wiley), chapter on solar geometry, including Cooper's declination equation
- Skin Cancer Foundation: guidance on seeking shade and sun protection
- U.S. Environmental Protection Agency: Sun Safety and the UV Index
How we write our guides: figures are typical US ranges checked against manufacturer documentation, published standards and installer pricing. Read our editorial standards. Spotted an error or outdated detail? Request a correction.