Weather & maps / Sun
Shadow Length Calculator (Any Place, Date, and Time)
Work out how long the shadow of a person, tree, fence, or building is from its height and the sun's elevation, worked out from the place, date, and time or entered directly, with the shadow's direction and a table through the day.
Shadow Length Calculator (Any Place, Date, and Time): Shadow length = height ÷ tan(sun elevation): at 45° a 2 m pole casts a 2 m shadow, and at 30° a 1.8 m person casts one of 3.12 m. The shadow points directly away from the sun, so its direction is the sun's azimuth plus 180°. Runs 100% locally in your browser with zero server file uploads.
- Category
- Everyday tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Place: London, United Kingdom · 51.51° N, 0.13° W · Europe/London
Shadow length = height ÷ tan(sun elevation): at 45° a shadow is as long as the object, at 30° about 1.73 times, and near sunrise and sunset it grows very long. The ground is assumed to be flat and level. Give a sun elevation directly, or let the page work it out from the place, date, and time.
Planning
Use the hourly table to see when a tree or a new extension will shade a garden bed or a neighbour's window, at the date you care about, such as the winter solstice.
The sun's position
For the sun's exact elevation and direction, use the sun angle calculator.
How to use it
- Enter the object's height.
- Choose the place, date, and time, or type a sun elevation.
- Read the shadow's length and direction, and the hourly table.
Privacy & limitations
Calculated in your browser; your location is saved only on this device.
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Frequently asked questions
Why are shadows longest in winter?
The sun stays lower in the sky, so the same object casts a longer shadow; at noon in midwinter in London the sun is only about 15° high, making shadows almost four times the height.
Does sloping ground matter?
Yes: the calculation assumes flat, level ground; a slope towards the shadow shortens it and a slope away lengthens it.
Can I find a height from a shadow?
Yes, reverse it: height = shadow length × tan(sun elevation), the method Thales is said to have used for the pyramids.
Free tool · runs in your browser · no account required