This topic has been discussed repeatedly on this forum. A lap should be only one way down the pool. Up and back is two laps. This being said, it is 96 (SCM) laps (or lengths) of the pool in 1.5 miles (approximately).
1 mile is 5280 feet. 3 feet per yard, 1.09 yards per meter. Therefore: 1615 meters per mile and ~2425 meters per 1.5 miles. That means 97 lengths in a 25 meter pool (which, no matter how much John exclaims, means 48.5 laps). Being nosy: Are you doing an open-water 1.5 mile race? Are you qualifying for something by distance? What the heck are you doing?
The more accurate conversion for a mile is 1609 meters (rounded to the nearest meter). Although the 1500 meter pool swim is commonly referred to as the "mile," this is actually slightly shorter than a real mile.
Again, refer to our previous discussions on "lap vs. length." When people fail to reach an agreement on what to call a lap, you can just refer to the distance, like 100, 500, 1500, etc...
It doesn't appear to be a matter of "agreeing", but rather it appears that John is unequivocally wrong:
See the definition for: Length/Lap
First of all, there are a million websites out there and most of them are WRONG.
According to your link, "...most coaches use the terms (lap and length) interchangeably..." This would lead me to believe that the answer to our question is quite equivocal.
This topic has been beaten to death already... it hurts me deeply to say this, but I can agree to disagree here.
Aight, aight, aight!! I'll settle this. I have a degree in mathematics and gruaduated Fagna bin Laden !!
1760 yards/mile divided by 1.094 yards/meter = 1608.76 meters/mile. 1608.76 meters/mile divided by 25 meters/length (of the pool) = 64.35 lengths/mile. 64.35 lengths/mile times 1.5 miles = 96.53 lengths.
So, screw "laps" BarryB44! Just swim "there" 48 times and "back" 48 times and then swim to the middle of the pool and stop there and celebrate.
Like running a lap on a track, "a lap" means to return the where you started. If you only go halfway around, it is not "a lap"...it's half a lap. So, in the pool (regardless of the pool's length) you have to go up and back (or back and forth as you say) for it to be a lap.
By the way, in the pool I regularly swim in its 25 laps/50 length for a mile. It's a 35 yard pool 50x35=1750 yards (10 yards short)
Definition of "lap" at http://www.thefreedictionary.com/lap
1. a. A part that overlaps. b. The amount by which one part overlaps another.
2. a. One complete round or circuit, especially of a racetrack. b. One complete length of a straight course, as of a swimming pool.
3. A segment or stage, as of a trip.
4. a. A length, as of rope, required to make one complete turn around something. b. The act of lapping or encircling.
5. A continuous band or layer of cotton, flax, or other fiber.
6. A wheel, disk, or slab of leather or metal, either stationary or rotating, used for polishing and smoothing.
It's kind of funny. I swam competetively for 12 years and swam 6- 10 miles per day. My event in college was the 500, 1000 and 1650 freestyle. The mile (in yards) is considered to be 1650 yds. I know that is not exactly right but that is still how it was and is today. Can someone explain that to me? I swam my first "mile" when I was 12 years old. It was (and still is) 66 lengths of the pool. When we spoke of laps, it was understood that lengths and laps of the pool were pretty much the same thing. A mile was 66 "laps." On the other hand, If I "lapped" my opponent, it was considered that I was passing him up after being 2 lengths ahead of him. Go figure.