You're that old and you need to know? Well... let's see, it depends on your height. After all, a 5 foot 42 year old shouldn't weigh the same as a 6 foot 42 year old. Do you now see why your question is flawed? I'm 65 and still don't know! LOL Seriously, as the above poster stated it depends on heigh and bone structure. Your doctor should be weighing you and telling you your correct weight when you go for your yearly physical. I'm unfortunately over-weight by 20 lbs., and have been on a good diet for 2 months and I'm losing that weight. As we grow older (especially women that have had children) the fat tends to stay around the waist, stomach, butt and upper legs.