The success of your garden depends on one primary factor: sunlight. Many gardeners plant “full sun” vegetables in the spring, only to realize by autumn that their house casts a massive 40-foot shadow that plunges their tomatoes into darkness. Understanding how the sun moves across the sky and how shadow lengths change between the summer and winter solstices is the key to productive gardening.
Use our Sun Path Calculator to determine the length of shadows cast by your home, trees, or fences. By calculating the solar altitude based on your latitude, you can scientifically map out the sunniest spots in your yard year-round.
Sun Path & Shadow Calculator
How to Use the Sun Shadow Calculator
- Object Height: Enter the vertical height of the object casting the shadow (e.g., your house roofline is typically 20-30 feet).
- Latitude: Your distance from the equator. For example, New York is ~40.7°, while London is ~51.5°.
- Season: Select “Winter Solstice” to see the “Worst Case Scenario” (longest shadows) or “Summer Solstice” for the peak growing season.
Why We Built This: The “Secret Sauce” of Year-Round Planning
The “Secret Sauce” of our tool is the Winter vs. Summer Comparison. Most people observe their yard in May when the sun is high and shadows are short. However, as we move toward the winter solstice, the sun’s angle drops significantly. In the Northern Hemisphere, a 20-foot house that casts a negligible shadow in June might cast a 60-foot shadow in December.
Our tool helps you realize if your “sunny” winter greenhouse location will actually be stuck in the shade of your neighbor’s fence.
Educational Guide: Solar Altitude and Plant Health
Plants require “Photons,” and the angle of the sun determines how many photons hit your leaves. When the sun is directly overhead (90°), the light is most intense. As the sun drops toward the horizon, the same amount of light is spread over a larger surface area, reducing intensity.
Planning for Full Sun
Most fruiting vegetables (tomatoes, peppers, cucumbers) require at least 6–8 hours of “Direct Sun.” Direct sun is generally defined as the period when the sun is more than 30° above the horizon. Use this calculator to ensure your planting beds aren’t blocked by structural shadows during these peak hours (typically 10 AM to 4 PM).
Greenhouse Placement
When placing a greenhouse for winter growing, you must account for the low winter sun. In many northern latitudes, the sun never rises higher than 20-25° in December. This means shadows will be nearly three times as long as the objects casting them. Always place your greenhouse on the south side of your property to avoid the “shadow reach” of your home.
Frequently Asked Questions
Q: What is Latitude and how do I find mine?
A: Latitude is your north-south position on Earth. You can find yours by typing “My Latitude” into Google or checking your weather app. Positive numbers are for the Northern Hemisphere; negative for the Southern.
Q: Why are shadows longer in the winter?
A: Because of the Earth’s tilt, the sun appears much lower in the sky during the winter months. A lower sun angle creates a more acute triangle between the sun, the object, and the ground, resulting in a longer shadow.
Q: Does the time of day matter?
A: Yes. This calculator determines the shadow length at Solar Noon, which is when the sun is at its highest point for that day (and shadows are shortest). Shadows will be significantly longer in the early morning and late afternoon.
