The number of laps a person must swim to reach 400 meters depends on whether he is swimming in a standard 25-yard, 25-meter pool or an Olympic-sized 50-meter pool. There are 22.860 meters in 25 yards, as one yard equals .91440 meters.

In a 25-yard standard pool, individuals need to swim 18 full laps to reach 400 meters. In a 25-meter pool, a person needs to swim 16 laps to reach 400 meters. Those swimming in Olympic-sized pools with lengths of 50 meters must swim a total of eight laps to reach 400 meters, which is approximately a quarter mile.