DH bought me a bracelet for my birthday. It's a little bit too small so he asked if I want to exchange it for the larger size which he said is only 6mm difference. I went on the website to have a look - there's 14.5cm, 17cm and 19.5cm options in length. The one he bought is 14.5cm. I pointed out that that makes it 2.5cm difference in length, not 6mm. He said yes, the length is 14.5cm but the diameter isn't. He has to calculate the diameter from the length to figure out the diameter 
Follow much heated discussion and disagreement. Why the hell does he need to know the diameter?! The length is on the website so you just measure your wrist using a tape measure! He said he had to measure the length against one of my bracelets then use Pi to find out the diameter and he's just been laughing at me like I'm a complete idiot by not understanding why.
I know this sounds like a mathematics exam question but I just want to know I'm not going mad!
YABU - you're wrong, your husband is really intelligent
YANBU - what the hell is he talking about?!
First world problem I know but it's just lighthearted!