I dont know if anyone here has posted anything about actually putting the 3/8 on their reel but I have 100 ft of 3/8 and 150 of 1/4 and my reel is so full it makes it hard to roll up properly I had a 100 foot and 150 foot sections of 1/4 before and only used up 2/3 of the reel. I would guess 100 ft of 3/8 is equal to 175 ft of 1/4 and that is not from trying to calculate it it is from real world experience.