Pilkington Sun Angle Calculator

Estimate sun paths for glazing, shading, and façade review. Compare altitude, azimuth, and shadows quickly. Create exportable angle reports for careful design checks today.

Sun Angle Calculator Form

Use 0 for flat upward glass and 90 for vertical glass.
Use 0 north, 90 east, 180 south, and 270 west.

Formula Used

Day angle: B = 360 / 365 × (N - 81)

Equation of time: EOT = 9.87 sin(2B) - 7.53 cos(B) - 1.5 sin(B)

Time correction: TC = 4 × (Longitude - LSTM) + EOT

True solar time: TST = Local time + TC / 60

Hour angle: HRA = 15 × (TST - 12)

Declination: δ = 23.45 × sin((360 / 365) × (284 + N))

Solar altitude: α = asin(sin φ sin δ + cos φ cos δ cos HRA)

Shadow length: Length = Object height / tan(altitude)

Incidence: θ = acos(cos Z cos T + sin Z sin T cos(Az - Saz))

The exposure factor uses the positive incidence cosine and glass transmittance.

How To Use This Calculator

  1. Enter the project latitude and longitude.
  2. Add the local date, time, and UTC offset.
  3. Enter the glass tilt and facing direction.
  4. Enter object height for a shadow check.
  5. Enter a transmittance value for planning review.
  6. Press the calculate button.
  7. Review the result above the form.
  8. Download CSV or PDF for project records.

Example Data Table

Location Date Time Latitude Longitude Tilt Surface Azimuth Use Case
New York 2026-06-21 12:00 40.7128 -74.0060 90 180 South glass summer review
London 2026-03-20 10:30 51.5074 -0.1278 90 90 Morning glare review
Sydney 2026-12-21 15:00 -33.8688 151.2093 90 270 Afternoon exposure review

Understanding Sun Angles for Glass Planning

Sun angle work helps designers judge daylight, heat, glare, and shade. A small change in latitude, date, or time can shift the sun path. That shift affects glass comfort and energy performance. This calculator gives a structured view of that movement. It is useful for early studies before final engineering review.

Why Solar Altitude Matters

Solar altitude is the height of the sun above the horizon. A high altitude usually creates shorter shadows. A low altitude creates longer shadows and more direct glare. This is important for windows, canopies, roofs, and outdoor screens. The value also helps compare summer and winter exposure.

Why Azimuth Matters

Solar azimuth shows the compass direction of the sun. It is measured clockwise from north. East facing glass usually receives stronger morning sun. West facing glass often receives stronger afternoon sun. South facing glass can be easier to shade in many northern hemisphere projects. The opposite pattern may apply in the southern hemisphere.

Glass Exposure Review

The incidence angle shows how directly sunlight strikes a tilted glass surface. A smaller incidence angle means stronger direct exposure. A larger angle means weaker direct exposure. The calculator combines tilt, surface direction, and solar position. It then estimates a beam exposure factor. This number is not a product rating. It is a planning value for comparison.

Shadow and Overhang Checks

Shadow length is estimated from object height and solar altitude. This helps review fins, parapets, nearby walls, and simple overhangs. The result changes fast near sunrise and sunset. Very low sun can create very long shadows. For that reason, design teams should test several dates and times.

Best Use Cases

Use this tool during concept design, façade review, classroom exercises, and quick site checks. Enter the project location first. Then compare equinox, solstice, and peak occupancy times. Save the result as a report. Export the data for records or team discussion. For final design, confirm results with local weather files, full simulation software, and professional glazing advice.

Practical Accuracy Notes

Use correct time zone offsets. Include daylight saving changes when they apply. Keep longitude signs consistent. Recheck inputs after moving a project between regions. Record assumptions beside every exported result before sharing.

FAQs

What does this sun angle calculator estimate?

It estimates solar altitude, azimuth, zenith, incidence angle, shadow length, and a simple beam exposure factor for glazing review.

Is this an official Pilkington tool?

No. It is an independent planning calculator for general sun angle studies. Use official product documents for final glass specifications.

What is solar altitude?

Solar altitude is the sun height above the horizon. Higher values usually create shorter shadows and stronger overhead exposure.

What is solar azimuth?

Solar azimuth is the sun compass direction. This calculator measures it clockwise from north for easier façade orientation checks.

How should I enter surface azimuth?

Use 0 for north, 90 for east, 180 for south, and 270 for west. Enter the direction the glass faces.

Why is shadow length sometimes unavailable?

Shadow length is unavailable when the sun is at or below the horizon. The tangent calculation cannot represent a useful shadow then.

Can I use this for final engineering?

Use it for early review and comparison. Final design should use validated simulation tools, local climate data, and professional advice.

What does beam exposure factor mean?

It is a simplified planning value. It combines direct incidence alignment with the transmittance percentage entered in the form.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.