Tropic of Cancer

Exactly where it is, and why it moves

On January 1, 2026, the Tropic of Cancer was at 23° 26′ 09.2″ N (23.43590° N). That latitude is the tilt of Earth’s axis relative to its orbit, which astronomers call the obliquity of the ecliptic.

The tilt isn’t fixed: right now it shrinks by about 0.47″ a year, as part of a cycle of roughly 41,000 years. So the Tropic of Cancer drifts about 14.4 m (south) every year, 0.9 mi (1.4 km) per century. We work it out with the International Astronomical Union’s formula for the mean obliquity (IAU 2006), the same one almanacs use.

On top of that slow drift there’s a small wobble called nutation, which shifts the tilt by up to 9.2″ either way over 18.6 years: about 280 m on the ground. Maps draw the line with the mean tilt, without the wobble.

Where the Tropic of Cancer runs

The Tropic of Cancer is 22,859 mi (36,789 km) long. 13,409 km of it runs over land (36%) and 23,372 km over the sea. That’s far more land than on the Tropic of Capricorn (24%), because the Northern Hemisphere holds more of the continents.

It crosses 18 countries and territories: Algeria, Niger, Libya, Chad, Egypt, Saudi Arabia, United Arab Emirates, Oman, India, Bangladesh, Myanmar, China, Taiwan, Mexico, Bahamas, Western Sahara, Mauritania, and Mali. Here’s the list in order, from the prime meridian heading east (it starts in Algeria, which the tropic is already crossing at 0° longitude).

From the Atlantic in Western Sahara to the Red Sea in Egypt it runs 3,271 mi (5,264 km) without touching the sea, almost all of it across the Sahara Desert. Along the way it grazes Chad, cutting just 3.3 mi (5.3 km) across its northern tip.

Western Sahara is a disputed territory, claimed by Morocco, which runs the western part, and by the Sahrawi Arab Democratic Republic. In India the tropic crosses eight states: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram.

Without touching land, it passes through Cuban waters, 12 mi (19 km) from the cays off the island’s north coast, and through U.S. waters, 9.3 mi (15 km) from Necker Island in Hawaii. Vietnam falls 4.8 mi (7.7 km) short: its northern tip doesn’t reach the line.

Cities near the Tropic of Cancer

The closest large city is Shantou (China), 4.4 mi (7.1 km) away. The closest capital is Muscat (Oman), 12 mi (20 km) away, followed by Dhaka (Bangladesh), 20 mi (32 km), and Havana (Cuba), 21 mi (33 km).

Straight-line distances on the ellipsoid from each city center to the tropic, along its meridian. “N” and “S” tell you which side it’s on.

The sun straight overhead: the June solstice

At the June solstice, around June 20 or 21, the noon sun is directly overhead everywhere along the Tropic of Cancer. At noon that day, things barely cast a shadow.

North of the tropic the sun is never directly overhead, not even in summer: it always stays a little to the south. Between the two tropics it passes overhead twice a year. That’s why the belt between them is called the tropics or the torrid zone: it gets the most sunlight.

The June solstice is the longest day of the year across the whole Northern Hemisphere. On the tropic itself, the December noon sun drops to just 43.1° above the horizon, so there are real seasons there.

Why it’s called the Tropic of Cancer

When it got its name, about 2,000 years ago, the sun was in the constellation Cancer at the June solstice. The Earth wobbles very slowly, like a spinning top (the precession of the equinoxes), and today the sun is in Taurus on that day. The name stuck anyway.

The word tropic comes from the Greek for “turning”: at the solstice the sun seems to stop on its way north and turn back.

Tropic of Cancer facts

Around 240 BC, Eratosthenes worked out the size of the Earth from the fact that in Syene, today’s Aswan in Egypt, the summer solstice sun stood directly overhead at noon. Today Aswan lies 45 mi (72 km) north of the tropic.

The tropic crosses Lake Nasser, the reservoir behind the Aswan High Dam, for 5.2 mi (8.4 km).

It crosses Mexico twice: first Baja California Sur and then, after the Gulf of California, the mainland from Sinaloa to Tamaulipas. Mexico City lies 275 mi (442 km) to the south, Havana 21 mi (33 km) to the south and Muscat, the capital of Oman, 12 mi (20 km) to the north.