The answer to that depends on two things: how you define a mile and the length of your pool.
Technically, a mile equals 1760 yards and 1609.3 meters.
For training purposes, most competitive swimmers and their coaches think of a mile as 1650 meters (remember, a mile is technically 1609.3 meters). But here’s where it gets admittedly weird: competitive swimmers also tend to call 1650 yards a mile, as well. Yes, technically this is 90 yards short of a mile.
In competitive swimming the “mile” event in a meet is either 1500 meters or 1650 yards, depending on whether the pool is measured in meters or yards.
Now that you have your definition of a mile and the length of your pool, plug your numbers into the below and refer to the formula ant to the side table below:
(Your definition of a mile) / (the length of your pool) = (# of laps you need to swim to swim a mile)
Thus, the answer to the question How many laps in an indoor swimming pool is a third of a mile?, are as follows:
Definition of a mile: 1500 (yards or meters)
no of laps of a 25 yard or 25 meter pool a third of a mile = 20
no of laps of a 50 yard or 50 meter pool a third of a mile = 10
Definition of a mile: 1650 (yards or meters)
no of laps of a 25 yard or 25 meter pool a third of a mile = 22
no of laps of a 50 yard or 50 meter pool a third of a mile = 11
Definition of a mile: 1760 (yards or meters)
no of laps of a 25 yard or 25 meter pool a third of a mile = 23.46
no of laps of a 50 yard or 50 meter pool a third of a mile = 11.73