How Far Is a Mile in Swimming Actually?

Units of measurement are manmade and to some extent arbitrary. Many have a lengthy history, and the mile is one of the longest standing units of measurement that continues to be something many of us interact with daily.

Today, the statute mile, also called a land mile, is equal to 5,280 feet, 1,760 yards, or 1.609 kilometers. But that hasn’t always been the case.

History of the Statute Mile

We have the Romans to thank for the mile, which derives from a unit of measurement they called the mille passum. That literally translates to 1,000 paces, each pace was five Roman feet. So, 5,000 Roman feet made up a Roman mile. Those Roman feet are a little shorter than our modern, 12-inch foot measurement, so the Roman mile equates to about 4,850 of our modern feet, according to the Encyclopedia Britannica.

By the early 1500s, the concept of an Old London mile emerged, and it was defined as 8 furlongs. At the time, a furlong (or furrow length) was defined as 625 feet, so the Old London mile equaled 5,000 feet.

However, “during the reign of Queen Elizabeth I, the mile gained an additional 280 feet,” Britannica reports, increasing to 5,280 feet as the result of a 1593 statute “that confirmed the use of a shorter foot that made the length of the furlong 660 feet.” That decree is what gave the land mile its name—the statute mile—and it’s the mile we still use today.

The Irish and Scottish, however, had their own, longer versions of the mile at the time, with the Irish mile clocking in at 6,720 feet (2.048 kilometers) and the Scottish mile at 5,952 English feet (1.814 kilometers).

The University of Nottingham reports that the mile was divided into furlongs, chains, yards, feet, and inches. These days, most people only use the yards, feet, and inches terms, but a furlong is still an important measurement in horse racing and agriculture. It’s equivalent to 1/8^th of a mile, which is 220 yards or 660 feet. Five furlongs measure about 1 kilometer and one furlong was the distance a team of oxen could plough a field without resting. An acre is one furlong long and one chain (66 feet or 22 yards wide).

The furlong used to be contested in swimming—the 220-yard freestyle was a marquee event at the 1904 Summer Olympics. That distance wasn’t contested again at the Olympic level but continued to be used in AAU and other competitions for some time. It was phased out in the mid-1900s when swimming pools shifted to more standardized 25 yards, 25 meters, or 50 meters, which made measuring a furlong more difficult. Nevertheless, USMS swimmer Willard Lamb still holds a state record in Washington for the 220 freestyle, which he set as a high school student in 1940. 

Nautical Miles

So that’s the story with land miles, but miles at sea are a little different. Naturally. Because why would it be simple?

A nautical mile is a little longer than a statute mile, equaling 1.852 kilometers or 1.15087 land-based miles. The measurement is based on the Earth’s longitude and latitude, with one nautical mile equaling one minute of latitude, the National Oceanic and Atmospheric Agency reports.

A 2023 Mental Floss article explained that a nautical mile “originally referred to one minute of arc along a meridian around the Earth. Think of a meridian around the Earth as being made up of 360 degrees, and each of those degrees consists of 60 minutes of arc. Each of these minutes of arc is then 1/21,600^th of the distance around the earth. Thus a nautical mile is 6,076 feet.”

Not complicated at all.

The nautical mile is used in seafaring and aviation because it’s “more practical for long-distance travel, where the curvature of the Earth becomes a factor in accurate measurement,” NOAA reports. “Nautical charts use latitude and longitude, so it’s far easier for mariners to measure distance with nautical miles. Air and space travel also use latitude and longitude for navigation and nautical miles to measure distance.”

The nautical mile is an international measurement that was officially set at 1.852 kilometers in 1929 by a group called the International Hydrographic Organization. At the time, the U.S. and the UK were using slightly different measurements for nautical miles, but the U.S. adopted the international nautical mile in 1954 and the UK followed suit in 1970.

Pool Miles

Now, when you head to the pool, are you swimming a nautical mile or a statute mile?

Neither, as it turns out.

And, actually, there are two different mile events in the pool that vary based on the size of the pool itself. Again, not complicated at all.

In a meters pool, the so-called mile event, also sometimes called the “metric mile” is 1,500 meters long. This is equivalent to 1,640.42 yards, a little short of the 1760 yards that make up a statute mile. It’s also well under the 2,025.37 yards that make up a nautical mile.

In yards pools—which are only a thing here in the U.S. because the rest of the world got together and decided to adopt the metric system a while back—the mile event is 1,650 yards long. It’s contested at the club, high school, and collegiate levels. Again, it’s short of the distance needed to cover an actual statute or nautical mile, but given typical pool sizing restrictions, it’s close enough and is a standardized distance with records going back decades.