Question: how many laps is 1 km swim?
Answer: The overly-simple answer is this: To swim 1650 yards in a pool measuring 25 yards you would need to do 66 lengths of the pool. In a pool measuring 50 yards you would need to do 33 lengths. You can use the same calculation for a 25 meter pool (66 lengths to swim 1650 meters, or 33 length of a 50 meter pool)