[ Fishing ] Open Question : How to measure this fish...My fiance just brought home a beautiful Rainbow Trout?

If I measure it from tip of tail to end of upper lip, it's 17 1/2 inches, but if I measure it from the tail to the end of the lower jaw it's 18 1/2 inches. It's was roughly 6 1/2 pounds (yay!) So which way do I measure this so he can brag properly?