The Tropic of Cancer is the furthest north the sun ever gets directly overhead. On the June solstice it's straight up at noon here and nowhere further north, which is the entire definition. Everything else about the line follows from that one fact.
Seventeen countries, three continents, and a remarkable amount of sand. The line runs through the Sahara, the Arabian Desert and the Thar, clips the Gulf of Mexico coast and finishes across southern Taiwan. The table below has every crossing with its entry and exit longitudes.
Two things are worth knowing before you read it. Mexico gets crossed twice, once in southern Baja California and again on the mainland north of Mazatlán, with the Gulf of California in between. And the Niger crossing is a sliver: the line clips the country's northern tip near the Algeria-Libya corner and that's it.
Worked out by intersecting the line with national borders, so the order is the order you’d meet them tracing the line west to east. Tap any row to fly the map to that crossing.
| # | Country | Enters and leaves | Distance |
|---|---|---|---|
| 1 | 990 km | ||
| 2 | 220 km | ||
| 3 | 210 km | ||
| 4 | 580 km | ||
| 5 | 380 km | ||
| 6 | 1,480 km | ||
| 7 | 20 km | ||
| 8 | 1,320 km | ||
| 9 | 1,070 km | ||
| 10 | 1,350 km | ||
| 11 | 370 km | ||
| 12 | 340 km | ||
| 13 | 2,230 km | ||
| 14 | 310 km | ||
| 15 | 560 km | ||
| 16 | 1,860 km | ||
| 17 | 130 km |
Natural Earth divides Western Sahara along the Moroccan sand berm. The coastal stretch the line crosses first is attributed to Morocco here and the stretch inland to Western Sahara, so both appear. Lists giving a single name for this crossing almost always say Western Sahara.
Add the Bahamas back in, and file the Moroccan-controlled stretch under Western Sahara, and the count lands on the 17 that most published lists give. The arithmetic matches. The names don't.
Latitudes here use the J2000.0 axial tilt of 23.4394°. The 2026 figure is nearer 23.4359°, which puts the real line about 390 m nearer the equator than the coordinates above, and it keeps shifting by roughly 14.5 m a year. No crossing changes hands over that distance.
These are real crossings that the 1:110 million borders can’t represent, listed here rather than quietly dropped. Small islands are almost always the reason. Add them to the computed table if you need a complete answer.
Look at the map and the pattern is hard to miss. Sahara, Arabian, Thar, and across the Pacific the Sonoran. The Tropic of Capricorn does the same in the southern hemisphere with the Atacama, the Kalahari and the Great Sandy. That isn't coincidence.
Air rises at the equator where the heating is strongest, sheds its moisture as it cools, drifts polewards at altitude, then sinks again at around 25 to 30° of latitude. Sinking air warms and dries. George Hadley worked the cell out in 1735 while trying to explain the trade winds, and its descending limb parks itself more or less on the tropics.
The exceptions prove interesting. The line crosses southern China and northern Myanmar as monsoon country, green and wet, because the Asian monsoon overwhelms the subtropical high every summer. Same latitude, completely different outcome.
The tropics are set by the tilt of the Earth's axis, and the tilt isn't constant. It oscillates between roughly 22.1° and 24.5° on a cycle of about 41,000 years, driven by the gravitational tug of the Moon and the other planets. We're in the shrinking half of that cycle.
In practice the Tropic of Cancer slides south by about 15 metres a year, or 0.47 arcseconds of latitude. Slow enough to ignore for a map, fast enough to matter for a monument. Several Mexican towns have had to relabel their tropic markers, and the markers on the southern equivalent have the same problem.
Baja California Sur has the best-known marker, a roadside monument on Highway 1 near Santiago. Los Cabos, an hour to the south, is genuinely in the tropics. La Paz, an hour north, isn't, and the drive between them crosses the boundary at a concrete sphere in the desert.
In Egypt the line crosses Lake Nasser about 70 km south of Aswan. Eratosthenes measured the circumference of the Earth around 240 BC from a well at Syene, modern Aswan, assuming the solstice sun stood directly overhead there. Nearly, rather than exactly: Aswan is north of the tropic, so his well had a small shadow in it. He came within a few percent anyway.
Taiwan has made a feature of it. There's a marker tower at Shuishang near Chiayi on the west coast and another at Fenglin in Hualien on the east, both set in small parks with the latitude painted across the ground.
The Indian crossing is the longest land stretch of the lot, more than 2,000 km through eight states: Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram. Ranchi sits about 10 km south of the line and Gandhinagar about 25 km, so both are inside the tropics by a margin you could walk in an afternoon.
The catch is resolution. Ten thousand points for the whole world means smoothed coastlines, islands that vanish entirely, and entry points that can sit 20 or 30 km from where a surveyor would put them, which is why distances are rounded to the nearest 10 km. The order of the countries is solid. The last digit of any single figure isn't. Crossings the data is too coarse to hold get named under the table rather than quietly folded in.