Sun Shade Angle Calculator

Calculator Inputs

Latitude

Longitude

UTC Offset

Date

Local Clock Time

Surface Azimuth

North 0, East 90, South 180, West 270.

Current Projection

Vertical Target Distance

Measure from shade line to the protected lower point.

Object Height For Ground Shadow

Length Unit

Formula Used

This calculator estimates solar position and shade geometry from physics based solar angles.

Day number: n = day of year.
Solar declination: δ = 23.45 × sin((360 ÷ 365) × (284 + n)).
Equation of time: E = 9.87sin(2B) - 7.53cos(B) - 1.5sin(B).
B angle: B = 360 × (n - 81) ÷ 364.
Time correction: TC = 4 × (longitude - standard meridian) + E.
Solar time: ST = local time + TC ÷ 60.
Hour angle: H = 15 × (ST - 12).
Solar altitude: α = asin(sinφsinδ + cosφcosδcosH).
Horizontal shadow angle: HSA = solar azimuth - surface azimuth.
Profile angle: PA = atan(tanα ÷ cosHSA).
Required projection: P = vertical target distance ÷ tan(PA).
Shadow drop: D = current projection × tan(PA).
Ground shadow: L = object height ÷ tan(α).

How To Use This Calculator

Enter the latitude and longitude of the project site.
Add the local UTC offset for the selected date.
Select the date and local clock time.
Enter the wall or window surface azimuth.
Add the existing overhang projection.
Enter the vertical distance that must be shaded.
Add an object height if you also need a ground shadow length.
Press the calculate button.
Review the profile angle, required projection, and coverage result.
Download the CSV or PDF file for your project record.

Example Data Table

Case	Latitude	Date	Time	Surface Azimuth	Projection	Vertical Target	Expected Use
Summer South Wall	34.00	2026-06-21	12:00	180	0.75 m	1.50 m	Overhang sizing
Morning East Wall	34.00	2026-04-15	09:00	90	0.60 m	1.20 m	Glare check
Afternoon West Wall	34.00	2026-09-10	16:00	270	0.90 m	1.80 m	Shade screen planning
Winter South Wall	34.00	2026-12-21	12:00	180	0.75 m	1.50 m	Solar access review

Understanding Sun Shade Angles

Sun shade design starts with the position of the sun. The sun changes height and direction through every day. It also changes through the year. A shade that works in June may fail in December. This calculator helps convert those sky positions into practical design numbers.

Why The Angle Matters

Solar altitude shows how high the sun is above the horizon. A high altitude creates a short steep shadow. A low altitude creates a long flat shadow. Solar azimuth shows the compass direction of sunlight. Wall orientation then decides whether the beam strikes the opening directly. The profile angle combines altitude with the horizontal difference between the sun and the wall.

Using The Result

The profile angle is useful for horizontal overhangs. When the sun faces the wall, a larger profile angle means a shorter projection can shade the same height. A small profile angle needs a deeper shade. If the sun is behind the wall, direct shade is not needed for that surface. The tool marks this condition clearly.

Design Notes

The calculator uses standard solar geometry. It includes declination, equation of time, solar time, hour angle, altitude, and azimuth. These values are estimates. Local hills, trees, nearby buildings, glass depth, and frame thickness can change the real shadow. Always check the final design on site. Use the result as a planning guide before detailed construction.

Better Comfort

Good shade design can reduce glare. It can also lower unwanted heat gain. This is useful for homes, classrooms, offices, workshops, and outdoor seating. South facing walls often use overhangs well in northern latitudes. East and west walls can need fins, screens, or adjustable shades because the sun is lower. The best solution usually combines geometry, comfort goals, and local climate.

Practical Planning

Test several dates and times. Compare summer, equinox, and winter cases. Check morning and afternoon hours. Save the result as a CSV file for records. Export a PDF when sharing with clients or team members. Keep units consistent. Measure the vertical distance from the shade line to the lowest point you want protected. Then compare required projection with your available depth.

Repeat checks after design changes, because small offsets can move shadows across glass.

FAQs

What is a sun shade angle?

It is the angle used to judge how sunlight reaches a surface. It helps estimate whether an overhang, fin, or shade can block direct rays.

What is solar altitude?

Solar altitude is the sun height above the horizon. Higher altitude creates steeper shadows. Lower altitude creates longer and flatter shadows.

What is solar azimuth?

Solar azimuth is the compass direction of the sun. This calculator uses north as 0 degrees, east as 90, south as 180, and west as 270.

What is profile angle?

Profile angle is the vertical shade angle seen on the wall plane. It combines solar altitude with the horizontal angle from the wall direction.

Why does wall orientation matter?

The same sun position can affect walls differently. A south wall, east wall, and west wall receive sunlight from different directions during the day.

Can this size a window overhang?

Yes. Enter the target vertical distance and compare required projection with current projection. The result shows whether the overhang covers the chosen point.

Why is the result sometimes not applicable?

This happens when the sun is below the horizon or behind the selected surface. In that case, direct shade is not needed for that surface.

Is this suitable for final construction?

Use it for planning and checking. Final construction should also consider local obstructions, frame depth, material strength, drainage, codes, and site measurements.