Awning Shade Calculator
Enter where you live, which way the wall faces and the awning's size, and see how far its shade reaches across the patio at any hour. It uses the same solar geometry as our city-by-city shade data.
Ground shade at this moment
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Through the day
| Solar time | Shade depth | Share of footprint shaded |
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How the shade calculation works
The calculator finds the sun's height (altitude) and compass direction (azimuth) for your latitude, date and time, using the standard solar declination and hour angle formulas. It then projects the shadow of the awning's front edge onto flat ground. What matters is the sun's profile angle: its height measured in the vertical plane at right angles to your wall. When the sun is off to one side, the profile angle is steeper than the actual altitude, which is why awnings shade surprisingly well when the sun is far around the corner, and poorly when it is low and straight ahead.
Worked example
A 10 ft awning on a 10 ft wall at 15° pitch reaches 10 × cos 15° = 9.7 ft out, and its front bar sits at 10 − 10 × sin 15° = 7.4 ft. If the sun's profile angle is 50°, the front-bar shadow lands 7.4 / tan 50° = 6.2 ft back toward the wall, so the shaded strip is 9.7 − 6.2 = 3.5 ft deep. Add a 12 in valance and the edge drops to 6.4 ft, which pushes the shade out to 9.7 − 5.4 = 4.3 ft.
Solar time versus clock time
Times are in local solar time, where 12:00 is the moment the sun is highest. With daylight saving time, solar noon in most of the US falls between roughly 12:45 and 1:45 pm on the clock, later in the western part of each time zone. If you sit outside at 5 pm by the clock in summer, check around 3:45 to 4:15 pm solar time.
What the model leaves out
- Side panels, trees, fences and neighboring buildings, which can add a lot of shade on east and west walls.
- Sloping ground. On a deck or patio that falls away from the house, shade reaches slightly further.
- Fabric light transmission. Shade under an open-weave or light-colored fabric is softer and brighter. See awning colors and heat.
- The sideways shift is reported for the front edge; the true shaded patch is a parallelogram, so the footprint percentage is an approximation.
For planning across a whole season, see our precomputed awning shade data for 14 cities, the guide to projection and pitch, and drop shades and solar screens for low-sun exposures.
Frequently asked questions
Why does my awning give almost no shade in the late afternoon?
On a west-facing wall the late afternoon sun is low and almost straight in front of the awning, so its rays pass under the front bar and the shadow falls back against the house. Extra projection helps only a little. A drop shade, solar screen or deep valance hanging from the front bar blocks low sun far more effectively.
Does a steeper pitch give more shade?
Usually yes, up to a point. Lowering the front bar moves the shadow outward, so more of the patio is shaded, especially when the sun is low. The limits are headroom (most people want the front bar at least 7 ft above the ground) and the awning's maximum pitch setting, which is commonly around 35 degrees.
What does "wall shade" mean in the results?
It means the sun is behind the wall the awning is mounted on, so the building itself is shading the area and the awning is not doing the work at that hour. On a west wall this is normal all morning; on an east wall, all afternoon.
Is this accurate enough to choose an awning size?
The solar geometry is accurate to well within a degree, which is far finer than awning size steps. The bigger uncertainties are your real mounting height, pitch and surroundings. Measure those carefully, and use the result to compare options rather than to promise shade to the inch.