Sunlight Exposure Calculator

About the Sunlight Exposure Calculator

The Sunlight Exposure Calculator is a professional visualization tool designed to help architects, engineers, urban planners, and solar energy professionals analyze how sunlight interacts with buildings throughout the day. This online tool simulates sun position, shadow behavior, and sunlight intensity, providing instant visual and numerical insights for optimal building design and solar panel placement.

How to Use the Calculator

1Set the location: Enter latitude and longitude or pick a city; the time zone fills in with daylight saving.
2Choose the date: Pick the day to analyze, such as the summer or winter solstice.
3Set the time: Move the time slider or press play to watch the sun move across the day.
4Describe the building: Enter the building height, the direction the surface faces and whether it is a wall, roof or ground.
5Read the results: See the sun's altitude and azimuth, the shadow length and the direct sunlight on the surface.

Understanding Sun Position Calculations

The calculator uses solar geometry formulas to determine sun position:

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

Hour Angle: H = 15° × (time - 12)

Solar Elevation: sin(α) = sin(lat) × sin(δ) + cos(lat) × cos(δ) × cos(H)

Shadow Length = Building Height ÷ tan(elevation)

These calculations account for Earth's tilt, rotation, and the observer's latitude to accurately predict sun position at any time and date. The tool visualizes this data in an intuitive canvas-based interface.

Key Metrics Explained

Sun Elevation (Altitude)

The angle between the sun and the horizon, measured in degrees. 0° means sun at horizon, 90° means sun directly overhead. Higher elevation = shorter shadows and more intense light.

Sun Azimuth

The compass direction of the sun, measured in degrees from North (0°). East is 90°, South is 180°, West is 270°. Determines shadow direction and which building facades receive direct sunlight.

Shadow Length

The distance from the building base to the shadow's end, calculated using building height and sun elevation. Longer shadows occur at low sun angles (morning/evening), shorter at midday.

Exposure Percentage

The amount of direct sunlight received by the selected surface (wall/roof/ground), accounting for sun angle and surface orientation. 100% means optimal direct exposure, 0% means no direct sunlight.

Light Intensity

The relative strength of sunlight, accounting for atmospheric absorption. Maximum at 90° elevation (sun overhead), decreasing at lower angles due to longer atmospheric path.

Applications

Architecture & Building Design

Optimize building orientation for natural lighting, minimize unwanted heat gain, design effective shading systems, and ensure adequate daylight in interior spaces.

Solar Panel Placement

Determine optimal panel orientation and tilt angle, identify shading issues, estimate daily energy production, and maximize solar efficiency throughout the year.

Urban Planning

Analyze shadow impact on neighboring properties, ensure adequate sunlight access for public spaces, comply with solar access regulations, and optimize street and park layouts.

Real Estate Analysis

Evaluate property sunlight exposure, assess natural lighting quality, identify optimal room placement, and understand seasonal variations in daylight.

Seasonal Variations

Season/Date	Sun Characteristics	Design Implications
Summer Solstice (June 21)	Highest elevation, longest day	Maximum solar gain, shortest shadows
Winter Solstice (Dec 21)	Lowest elevation, shortest day	Minimum solar gain, longest shadows
Equinoxes (Mar 21, Sep 21)	Moderate elevation, equal day/night	Balanced conditions, transitional design

Optimal Building Orientations

Northern Hemisphere

South-facing (180°) walls receive maximum sunlight year-round. Ideal for passive solar heating in winter. North-facing walls receive minimal direct sun, suitable for spaces requiring consistent, indirect light.

Southern Hemisphere

North-facing (0°) walls receive maximum sunlight. Design principles are inverted compared to Northern Hemisphere. East and west orientations similar in both hemispheres.

East-West Orientation

East-facing (90°) receives morning sun, west-facing (270°) receives afternoon sun. West exposure typically warmer due to accumulated daily heat. Consider shading for west-facing windows in hot climates.

Shadow Analysis Guidelines

✓Analyze shadows at critical times: 9 AM, 12 PM, and 3 PM for comprehensive understanding
✓Consider both summer and winter solstice conditions for year-round analysis
✓Account for neighboring buildings and trees that may cast additional shadows
✓Verify shadow impact on outdoor spaces, gardens, and solar panels
✓Check local regulations regarding shadow restrictions on adjacent properties
✓Use animation feature to visualize shadow movement throughout the day

Frequently Asked Questions

How accurate are the sun positions?

The calculator uses standard solar geometry with the equation of time, which is accurate to within about 1° for planning. It does not model atmospheric refraction near the horizon, clouds, terrain or surrounding buildings.

Which way should solar panels face?

In the Northern Hemisphere, due south (180°) with a tilt close to the latitude gives the most energy over a year; in the Southern Hemisphere, due north. East- or west-facing panels produce about 10–20% less but shift output to the morning or evening.

How long is a building's shadow?

Shadow length = height ÷ tan(sun altitude). In New York at noon on the winter solstice the sun is about 26° high, so a 10 m (33 ft) building casts a shadow about 20 m (67 ft) long.

How do I use this for passive solar design?

Check the low winter sun to place windows that let in heat, and the high summer sun to size overhangs that shade them. At 40° N the noon sun is about 73° high at the summer solstice and 26° at the winter solstice.

Does it account for daylight saving time?

Yes. For preset cities the UTC offset follows the local rules for the chosen date, and you can set any offset by hand for other places.

Design Best Practices

Maximize Natural Light

Orient main living spaces toward the sun's path. Use clerestory windows for deep light penetration. Consider light shelves to bounce daylight deeper into rooms.

Control Solar Heat Gain

Design overhangs sized to block summer sun while admitting winter sun. Use deciduous trees for seasonal shading. Consider low-E glazing for west-facing windows.

Optimize Solar Panels

Ensure panels face optimal direction with appropriate tilt. Minimize shading from chimneys, vents, or nearby structures. Consider seasonal sun path variations.

Respect Neighbors

Analyze shadow impact on adjacent properties. Comply with solar access regulations. Consider setbacks and building height to minimize overshadowing.

Why Use This Calculator?

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Real-Time Visualization

Instant visual feedback with animated sun movement and shadow projection

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Accurate Calculations

Based on solar geometry formulas used in professional applications

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Global Coverage

Works for any location worldwide with preset cities for convenience

Professional Sunlight Analysis Tool

This calculator is designed for architects, engineers, urban planners, and solar energy professionals who need quick and accurate sunlight exposure analysis. It combines scientific solar position calculations with intuitive canvas-based visualization, making complex sun path analysis accessible while maintaining professional-grade accuracy. We do not collect or store what you enter. Use this tool for preliminary analysis and conceptual design, and consult with professionals for detailed engineering and compliance verification.

Location

Building

Time Control

Location Presets