History, Masters, Misc.

Why is a “pool mile” not an “actual mile”?

If you are not a swimmer, you may not be aware of the fact that swimmers in the US swim for 1650 yards and call it a mile. If you are a swimmer in the US, you may not be aware of the fact that what you are calling a mile, is not actually a mile. In fact, it’s 110 yards short of a mile.

mile in yards

Finding an explanation for this was not easy. The most “thorough” answer I could find seems to be this blog post, but reading and re-reading it, there is information missing that makes it almost impossible to decipher. So, combining information gleaned from this post with other information found through Internet research (there’s not a lot out there on this subject), I have put together the following summary. If you are reading this, and you see something I have written that you know to be inaccurate, PLEASE TELL ME IN THE COMMENTS SECTION.

Summary explanation:

–> “Long course” pools in the US used to be 55 yards, which made swimming a “mile” and “half mile” easy and convenient.  So, for a long time, the official mile distance in the United States was 1760 yards (16 long course laps), which is accurate.

–> International distance “long course” meets, including the Olympics, are swum in a 50 meter pool (1 foot shorter than 55 yards). For the sake of our Olympic athletes, the US changed its “long course” pools to 50 meters, but kept our short course pools at 25 yards (schools and community centers couldn’t afford to remodel their pools).  I haven’t found an explanation for why our short course pools were ever built as 25 yards to begin with.

–> 1500 meters (1.5k) is the standard international race length (1640 yards), and Americans commonly (though inaccurately) refer to this distance as “the mile.”

–> To keep our athletes (who are often training in 25 yard pools) international-competition ready, the United States came up with a new event, the 1650 yard freestyle, which is very close to the international 1500 meter (1640 yards).  Since we called the 1500 meter swim “the mile,” the name stuck to the 1650 yard swim, even though it is 110 yards shy of an actual mile.

Got it?

Of course, my favorite comment on an internet forum:

“Since you are in the water, you should swim a nautical mile anyway which is about 2000 yards or 80 lengths.”

[Further research uncovers this interesting information: The nautical mile is measured as one minute of arc of latitude along any meridian. This is convenient for the navigators of boats—and planes—as ocean charts are often based on the Mercador projection, whose scale varies from the equator to 80° north or south latitude. But, of course, measuring miles by degrees of latitude is also imperfect, as the earth is not exactly spherical, and the nautical mile is longer as you get closer to the poles. For that reason, international committees agree on a set distance for the nautical mile as 1,852 meters.]


About Caitlin Rosen



9 thoughts on “Why is a “pool mile” not an “actual mile”?

  1. This was really great and clarified a few questions I had for years which I never researched myself!

    Posted by Tom Malone | April 13, 2011, 5:07 am
  2. While I knew it was 1760yds for the mile, I had no idea on the other history. Pretty cool. Thanks for sharing!

    Posted by Jen Davino | April 13, 2011, 9:29 am
  3. Thank you! I was beginning to think “How many laps in my 25-yard pool is a mile?” was the question that stumped the internet! Now I just have to decide if I want to do 66-lap “swim miles” or 70-lap “land miles”. Ah, the temptation…

    Posted by stvrsnbrgr | May 2, 2014, 8:03 pm
  4. Reblogged this on Dr Jill's swim blog.

    Posted by minkejill | August 29, 2014, 9:26 am
  5. Thanks for sharing and for your insightful research. I have had more than a couple disagreements, regarding this, with the lifeguards at the pool where I swim. They were convinced that 66 laps was a mile. Even when I showed them the math, they just scratched their collective heads. It mattered/matters to me because I am trying to swim the length of the USA, 2100 miles. Currently I am at 1563 miles and hope to finish next spring. I can give you some helpful advice regarding your shoulder problems, if you’re interested.

    Posted by Dennis | January 21, 2015, 3:26 pm
  6. Could it also be that a mile is 1609 METERS, so if swimming in a meter pool (most swim in a 25 meter pool so 50m is down and back) you have to swim 1650 METERS to swim a mile as you won’t be stopping in the middle of the lane. Could it simply be that people don’t know a meter from a yard?

    Posted by Todd | July 14, 2017, 12:09 pm
  7. Caitlin, as an endurance and open water swimmer. I found all of your observations accurate. I do have a suggestion as to the origins of the 25-yard long pool standard. Just as basketball was invented at a Massachusetts YMCA, there is a history that may indicate that the 25-yard length was established by the YMCA as well. Late 19th and early 20th century public and school pools were not of a uniform length or width, but “Y” pools were 25-yards long.

    This information was delivered to me as a child and may have been anecdotal, but my experience and observations do not contradict anything that I had been told. With that being said, there is an exception to everything, and I believe there also are a few early “Ys” that have pools that are only 20-yards long.

    Posted by wordmorpher | July 7, 2018, 8:15 pm


  1. Pingback: Saturday Long Swims « Throw Me In The Ocean - April 13, 2011

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About Me

Caitlin Rosen I learned to swim as a wee one from my dad, who didn't really swim himself, but was tall enough and encouraging enough to send me back and forth to the side of a pool. There were also the terrifyingly wonderful trips on his shoulders out into crashing ocean surf, which instilled in me a fear and respect for the rising and falling, tempestuous beast, on whom he repeatedly admonished us kids to never, ever turn our backs. Read more...

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