Contents
- What Is the Longest Straight Line You Can Walk Without Crossing Water?
- The Water Route Everyone Already Knows, and the Reddit Post Behind It
- Route One: Liberia to Wenzhou, the Version Most Sites Repeat
- Route Two: Quanzhou to Sagres, the Original Paper's Route
- Liberia–Wenzhou vs Quanzhou–Sagres, Side by Side
- Why the Two Numbers Don't Match
- A Third Number in the Mix: The 2024 Shitangzhen Story
- Who Ran the Numbers, and How It Started
- Frequently Asked Questions
There are two “longest straight lines on land” floating around online, and most articles about either one never mention that the other exists. One route runs from Liberia to Wenzhou, China — roughly 13,573 to 13,589 km through 18 countries. The other, the one that actually shows up in the original 2018 research paper, runs from Quanzhou, China to Sagres, Portugal — 11,241 km through 15 countries. Both numbers are real; they just come from two different lineages of the same question.
What we checked ourselves
The figures below were not taken from other articles. We checked them ourselves on 2026-09-14 16:40.
Recalculating the great-circle distance directly from the published coordinates, the Liberia (Greenville)–China (Wenling) 'longest straight line on land' works out to 13,574.1km when the Earth is treated as a sphere (mean radius 6371km), and 13,588.4km on the WGS84 ellipsoid (Vincenty formula) — a gap of roughly 14km (9 miles) between the two calculation methods.
Method: We took the precise coordinates of the two endpoints as given in Wikipedia's 'Extremes on Earth' entry (Liberia 5°2′51.59″N 9°7′23.26″W; near Wenzhou, China 28°17′7.68″N 121°38′17.31″E) and calculated the distance directly in Python using three methods: (1) the Haversine formula (spherical, with two radii, R=6371km and R=6378.137km) and (2) the Vincenty inverse formula (WGS84 ellipsoid). We calculated the Portugal (Sagres, 37°02′N 8°55′W)–Quanzhou, China (24°33′N 118°38′E) segment the same way.
| Segment | Calculation method | Calculated result | Originally published value |
|---|---|---|---|
| Liberia–China (Wenling) | Sphere, R=6371km (mean radius) | 13,574.1km / 8,434.6mi | Amusing Planet: 13,573km / 8,434mi |
| Liberia–China (Wenling) | Sphere, R=6378.137km (equatorial radius) | 13,589.3km / 8,444.0mi | Offbeat Travelling: 13,589km / 8,443mi |
| Liberia–China (Wenling) | WGS84 ellipsoid (Vincenty) | 13,588.4km / 8,443.4mi | Wikipedia: 13,588km / 8,443mi |
| Portugal (Sagres)–China (Quanzhou) | Sphere, R=6371km | 11,240.3km / 6,984.4mi | Chabukswar & Mukherjee paper: 11,241km / 6,984.9mi |
| Portugal (Sagres)–China (Quanzhou) | WGS84 ellipsoid (Vincenty) | 11,260.3km / 6,996.8mi | (No published value using this method) |
Caveat: the coordinates themselves are rounded to degrees(°)-minutes(′)-seconds(″) in each source article and paper, so sub-decimal errors are baked in. We also did not reproduce the terrain-elevation check (the original paper's algorithm for determining whether the line 'stays on land' using the ETOPO1 terrain model) — here we only recalculated the pure geometric shortest distance between the two points.
Even using the exact same pair of coordinates (near Liberia and near Wenling, China), three outlets have published three different distances — 13,573km, 13,588km and 13,589km — a gap of up to 16km (about 10 miles).
Method: we opened the Amusing Planet, Wikipedia (Extremes on Earth) and Offbeat Travelling articles directly and compared, side by side, the km/mi figures each one gives for the same Liberia-China straight line. The recalculation above confirms this gap is not a typo but is reproduced directly by the difference in calculation model — treating the Earth as a 'sphere' versus a 'WGS84 ellipsoid'.
| Source | Published distance |
|---|---|
| Amusing Planet | 13,573km (8,434mi) |
| Wikipedia, Extremes on Earth | 13,588km (8,443mi) |
| Offbeat Travelling | 13,589km (8,443mi) |
| Our recalculation (sphere, R=6371km) | 13,574.1km |
| Our recalculation (WGS84 ellipsoid) | 13,588.4km |
Caveat: the sample was limited to three outlets. We could not fully confirm which Earth model the original paper (Chabukswar & Mukherjee, arXiv:1804.07389) actually used, as we did not cross-check the full text of the paper — here we estimated it based on how closely the published figure matches our recalculated values.
What Is the Longest Straight Line You Can Walk Without Crossing Water?
There isn’t a single agreed number. There are two. The version most travel and geography sites repeat is Liberia to Wenzhou: about 13,573 to 13,589 km (roughly 8,434 to 8,443 miles) across 18 countries and 9 time zones. The version that comes from the actual 2018 academic paper on the topic is Quanzhou to Sagres: 11,241 km (about 6,985 miles) across 15 countries.
Neither one is fake. They’re not the same route, though — plenty of coverage treats them as interchangeable, and that mix-up is why this question keeps generating confused search results.
The Water Route Everyone Already Knows, and the Reddit Post Behind It
You’ve probably seen the ocean version already — it circulates as a map every so often. That route runs from Sonmiani, in the Las Bela district of Balochistan, Pakistan, all the way to the Karaginsky District of Kamchatka Krai, Russia. It’s about 32,089.7 to 32,090 km long, though the mile conversion varies a bit by source: 19,939.62 miles from MIT Technology Review and gCaptain, 19,940 miles from Guinness World Records, and 19,910 miles from Amusing Planet.
The path threads the Arabian Sea, the Indian Ocean, the Mozambique Channel between Africa and Madagascar, around the Cape of Good Hope, then between Antarctica and Tierra del Fuego near Cape Horn, before running north into the Pacific. Guinness World Records lists it as the longest straight line that can be sailed, record ID 15-113423.
Here’s the part fewer people know. The idea didn’t start with a research team. A Reddit user going by “kepleronlyknows” posted a map of this exact path to r/MapPorn back in 2012, arguing it was the longest straight line you could sail without hitting land. The precise date of that post isn’t confirmed. Six years later, researchers ran the actual math and found the claim held up.
This water route shows up in map roundups and trivia lists on repeat. Its land counterpart rarely gets mentioned in the same breath — which is strange, since it’s the more confusing of the two.
Route One: Liberia to Wenzhou, the Version Most Sites Repeat
This is the answer you’ll find in most general write-ups, including the version that made its way into Wikipedia-style summaries.
- Start: the West African coast in Liberia, near Greenville, about 250 km southeast of Monrovia.
- End: an area near Wenzhou, Zhejiang province, China. Sources describe it differently — some put it about 100 km northeast of Wenzhou proper, others describe an industrial town roughly 320 km south of Shanghai.
- Distance: 13,573 km according to widely repeated summary figures (the original Big Think article this traces back to couldn’t be directly verified — the page returned an access error), or 13,589 km according to Offbeat Travelling. That’s roughly 8,434 to 8,443 miles.
- Countries and regions crossed: 18 in total — Liberia, Ivory Coast, Burkina Faso, Ghana, back through Burkina Faso, Niger, Chad, Libya, Egypt, Israel, the West Bank, Jordan, Iraq, Iran, Turkmenistan, Uzbekistan, Tajikistan, Afghanistan, back through Tajikistan, and finally China.
- Time zones: 9.
- No ocean is crossed, though the line does pass over some rivers and lakes along the way.
This is the number you’ll see cited most often. It is not, however, what the original researchers calculated.
Route Two: Quanzhou to Sagres, the Original Paper’s Route
This is the route that actually appears in the 2018 paper by Rohan Chabukswar and Kushal Mukherjee — the same paper that verified the Pakistan-to-Kamchatka water route.
- Start: Quanzhou, China.
- End: near Sagres, on the southwestern tip of Portugal.
- Distance: 11,241 km, about 6,984.9 miles.
- Countries crossed: 15.
There’s a detail worth flagging here, because it trips people up: several secondary sources pair Sagres with Wenzhou, as if it’s one route described two ways. That’s not accurate. Sagres pairs with Quanzhou in the original paper’s version; Wenzhou pairs with Liberia in the more widely cited version. Two separate route pairs that happen to end in roughly the same part of China.
Liberia–Wenzhou vs Quanzhou–Sagres, Side by Side
| Liberia → Wenzhou | Quanzhou → Sagres | |
|---|---|---|
| Start point | Near Greenville, Liberia | Quanzhou, China |
| End point | Near Wenzhou, Zhejiang, China | Near Sagres, Portugal |
| Total distance | 13,573–13,589 km (~8,434–8,443 mi) | 11,241 km (~6,985 mi) |
| Countries crossed | 18 | 15 |
Why the Two Numbers Don’t Match
Here’s what’s actually confirmed. The original 2018 paper’s calculation produced the Quanzhou-to-Sagres result: 11,241 km, 15 countries. Separately, the figure that ended up widely quoted across media and reference sites is the Liberia-to-Wenzhou result: 13,573 to 13,589 km, 18 countries.
What isn’t confirmed is why they differ — no source lays out the exact methodological reason, whether that’s coastline data resolution, different reference points for where a “country” starts and ends, or a different dataset version entirely. My guess is coastline resolution: a lower-quality coastline dataset can shift a start or end point by tens of kilometers without anyone intending it to. It’s a hunch, not a citation.
A Third Number in the Mix: The 2024 Shitangzhen Story
Just to make things messier, a January 2024 article from That’s Mags describes a version of this same general route — China down to Liberia — but names the Chinese starting point differently: Shitangzhen, a town south of Taizhou in Zhejiang province, not Wenzhou itself. That piece states the China-only segment of the route is 589 miles, but it doesn’t give a total end-to-end distance.
Whether that 589 miles folds into the 13,573/13,589 km Liberia-Wenzhou total, or is a separate number altogether, isn’t clear.
Who Ran the Numbers, and How It Started
Both the water route and the original land route (Quanzhou to Sagres) trace back to the same 2018 paper: “Longest Straight Line Paths on Water or Land on the Earth,” by Rohan Chabukswar of the United Technologies Research Center in Ireland and Kushal Mukherjee of IBM Research in India. It’s catalogued on arXiv as 1804.07389, submitted April 9, 2018, and revised July 2, 2018, filed under the math.HO (history and overview) category.
Their method was a branch-and-bound algorithm — a search technique that cuts off unpromising paths early instead of testing every possible line on Earth’s surface one by one. That’s what let them confirm, mathematically, that the 2012 Reddit map really was the longest sailable straight line, and separately calculate the Quanzhou-Sagres land answer.
Frequently Asked Questions
Is Liberia-to-Wenzhou or Quanzhou-to-Sagres the “real” answer? There’s no single official standard here. Quanzhou-to-Sagres is what the original 2018 paper calculated; Liberia-to-Wenzhou is the figure that went on to get cited everywhere else. Which one counts as “the” answer depends on whether you trust the source paper or the number that spread.
Who calculated these routes, and how? Rohan Chabukswar (United Technologies Research Center, Ireland) and Kushal Mukherjee (IBM Research, India), using a branch-and-bound algorithm, published as arXiv paper 1804.07389 in 2018.
Does the land route cross any water at all? Not ocean. According to Amusing Planet, the Liberia-Wenzhou line does cross some rivers and lakes along its path, even though it avoids the sea entirely.
How does the land route compare to the water route in length? The water route, Pakistan to Kamchatka, is roughly 32,089.7 to 32,090 km — more than double either land figure. Both cited land route figures, 13,573–13,589 km and 11,241 km, come in well under half of that, though exact mile conversions differ by source for both categories.
What strikes me most is how this happened at all: a number that never appears in the original paper became the “famous” one, while the paper’s actual answer got sidelined. That’s a pattern worth watching for in other viral geography facts, not just this one. For now, the honest move is to name both routes and say which lineage each comes from, rather than picking a winner.
Image credits
- Photo by Bert Christiaens on Pexels