How many miles do you have to fly around the world?

Around the equator, the answer is 24,901 miles — 40,075 km. But almost nobody flies the equator, and a real round-the-world itinerary is usually a good deal shorter than that. London–New York–Los Angeles–Tokyo–Dubai–London is a genuine circumnavigation, and it is 19,725 miles: 31,745 km, or 79% of a lap.

That gap is the whole story, and it catches people out because a globe is not a map.

Why a circumnavigation can be shorter than the equator

The equator is the largest circle you can draw on the Earth. Every other circle of latitude is smaller, and they shrink fast — the length of a parallel falls off with the cosine of its latitude. At 60° north, a complete circle around the planet is 20,038 km: exactly half the equator. At 80° north it is under 7,000 km.

Airline route maps live in the northern mid-latitudes because that is where the cities are. London sits at 51.5° N, Tokyo at 35.6° N, New York at 40.6° N. A loop through those is a loop around a circle meaningfully smaller than the equator, which is why the arithmetic comes out below 40,075 km without anyone cheating.

Here is the same trip drawn several ways, all of them real airport pairs, all great circle distances:

The last one is the longest, and the reason is that it dips deep into the southern hemisphere. Sydney is at 33.9° S. Going down there and coming back adds latitude to a trip that is otherwise trying to stay on one band, and you pay for it in distance.

The official minimum, and why it exists

Taken to its conclusion, the shrinking-parallel trick is absurd: you could "circle the world" in a few hundred kilometres by flying a tight loop around the North Pole, crossing every meridian on the way.

So the record books define it away. The Fédération Aéronautique Internationale, which ratifies aviation records, requires a round-the-world flight to cross all meridians and to cover a course of at least 36,787.559 km — 22,859 miles. That figure is not arbitrary: it is the length of the Tropic of Cancer, at 23.4° north. Fly a genuine circumnavigation at any latitude closer to the equator than that and you clear the bar automatically.

Note where the airline itineraries above land relative to it. Most of them are under the FAI minimum. They are round-the-world trips in the ordinary sense — you leave heading west, you come back from the east, you cross every line of longitude — but they would not qualify as a record circumnavigation.

What this means for your own total

If you are counting how many times around the Earth you have flown, the honest denominator is 40,075 km, because that is the number the comparison is worth making against. A lap is a lap of the planet at its widest, not a lap of whichever parallel your route happened to sit on.

It does mean the first lap arrives sooner than the phrase suggests. One round-the-world trip does not get you to one lap. Two does, comfortably.

A few reference points, all great circle:

• London – New York: 5,570 km
• London – Singapore: 10,885 km
• Los Angeles – Tokyo: 8,800 km
• Singapore – New York: 15,350 km

You can check any pair against the full airport table, or look at the longest scheduled routes if you want the extreme end of it.

The other reason the map lies

None of the distances above look right on a flat map, and that is not a rendering problem — it is what happens when you flatten a sphere. The Mercator projection preserves angles and destroys area, so a route across the top of the world looks like a wild detour and a route along a parallel looks like the obvious straight line. On a globe it is the other way round.

That is why long-haul flights go over Greenland, and it is the same effect that makes a northern circumnavigation come out shorter than your intuition says it should.

Orbit works out great circle distance from 8,801 airports and keeps your running lap count. Download now.