Photo courtesy of Jesse Skoubo of the Gazette-Times of Jordan Selker holding a lap counter for Brandon Shreeve in Corvallis, Oregon.

Open water swimmers often train in pools as well as in lakes and oceans.

Marathon swimmers and competitive pool swimmers are known for doing tough sets like 100×100 in 25-yard, 25-meter or 50-meter pools.

But the question was raised – and answered comprehensively – by Evan Morrison, how far is a “lap” of a pool?

Is a lap one full length of a pool (no matter its length) or does a lap refer to two lengths of the pool? Morrison gives a comprehensive review of the term here.

“Some people who I workout with, say that a 400-meter swim in a long-course 50m pool is 4 laps and there are 10 laps to a 500-yard swim which is 20 lengths of a 25-yard pool,” says Steven Munatones. “But I grew up in Southern California where competitive swimmers refer to one lap as one length of a pool. It is most often seen during competitive swimming competitions in the distance freestyle race where swimmers are reminded of the number of lengths of the pool they have swum with lap counters.

Competitive swimmers and coaches count 20 laps for a 500-yard swim in a 25-yard pool and 30 laps for a 1500-meter freestyle in a 50m pool. That is how I was taught back in the 1960s and 1970s.

Plus, if a lap is defined as two lengths of a pool, how do you define one length of a pool? A half-lap?“

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