Solar Noon Shadow Length Calculator - Shadow Length at Midday

Use the free tool below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.

What solar noon really is

Solar noon is not 12 o’clock. It is the moment the Sun crosses your local meridian, the imaginary line running from north to south through your position, and reaches its highest point for the day. Clock noon and solar noon differ because time zones are wide, daylight saving shifts the clock, and Earth’s orbit is not a perfect circle.

This calculator finds solar noon for any date, latitude, and longitude, then turns it into shadow lengths. Enter the date, your coordinates, and the height of an object, and the tool returns the Sun’s altitude at solar noon, the shadow length at solar noon, and the shadow at an hour of your choice. Shadow length is simple trigonometry: height divided by the tangent of the Sun’s altitude. A 2 metre person under a Sun 45 degrees high casts a 2 metre shadow. Under a Sun 62 degrees high, the shadow shrinks to about 1.06 metres. Under a low winter Sun, it stretches far longer.

Why shadows change so much

Two things control shadow length: the time of day and the season. At solar noon the Sun is highest and shadows are shortest. Near sunrise and sunset the Sun is low and shadows stretch enormously, which is why photographers love those hours and why a fence that casts no shadow at noon throws a long stripe across the garden in the evening. Season matters just as much: the Sun climbs much higher at noon in summer than in winter, so the same object casts a short shadow in June and a long one in December, at the same place and the same clock time.

Latitude sets the whole range. Near the equator the Sun passes almost overhead at noon for part of the year, and shadows nearly vanish. At high latitudes the Sun never climbs far, even in summer, so shadows stay long all year.

A worked example

Take a 2 metre person in London on 21 June. Solar noon falls just after 1 pm by the clock in summer time, the Sun reaches about 62 degrees, and the shadow is about 1.06 metres long, pointing north. Take the same person in London on 21 December, and solar noon brings the Sun to only about 15 degrees, giving a shadow of about 7.5 metres, also pointing north but stretching far across the ground. The person did not change, the place did not change, and only the season changed, yet the shadow grew sevenfold. Anyone planning a garden, a fence, or a solar panel that must avoid shade needs both numbers, not just the summer one.

Now try the hour-of-day option. At 9 am on that June day the Sun is lower, so the same person casts a longer shadow, pointing north-west, and by 6 pm the shadow is long again, pointing north-east. Shadows rotate through the day as the Sun moves, which is the whole principle of a sundial.

Practical uses

Garden planning: check whether a new tree or fence will shade a vegetable bed at noon in summer, when shade matters most.
Solar panels: a panel shaded even partly at solar noon loses far more power than the shaded area suggests, so check the noon shadow first.
Photography: long shadows near sunrise and sunset add depth to landscapes, while the short noon shadow flattens them.
Building design: window overhangs are sized from the summer noon Sun angle, so rooms stay cool in summer and gain heat in winter.
Sundials: a sundial only works if it is set for true north and your latitude, because solar noon, not clock noon, is its reference.

Limits to keep in mind

The calculator assumes a flat horizon. A hill, a building, or a tree line to the south blocks the Sun earlier than the maths suggests and lengthens the effective shadow. It also assumes the Sun is a point, while the real Sun is a disc, so shadow edges are slightly soft rather than razor sharp. Near the poles, solar noon behaves oddly: in polar summer the Sun never sets, and in polar winter it never rises, so the tool reports the Sun below the horizon instead of inventing a shadow. Those are edge cases, but they are the honest answer for those latitudes.

Frequently asked questions

Why is my shadow not shortest at 12 o’clock? Because clock time is a political compromise. Time zones, daylight saving, and Earth’s elliptical orbit all push solar noon away from 12, sometimes by more than an hour.

Which way does a noon shadow point? Away from the Sun. In the northern hemisphere outside the tropics, the noon shadow points north. In the southern hemisphere it points south. Between the tropics it can point either way depending on the season.

Can I measure my own latitude from a shadow? Yes, roughly. Measure a vertical stick and its noon shadow, work out the Sun’s altitude from the ratio, and combine it with the known solar declination for the date. The calculator does the reverse of that classic exercise.

Use the calculator above before you build, plant, or install anything that lives by sunlight: enter your date and coordinates, read the noon shadow and the hour you care about, and plan for the longest shadow, not just the shortest.

Solar Noon Shadow Length Calculator – Shadow Length at Midday