Measurements for Backpacking?

After reading a few of the posts, I keep seeing a lot of emphasis on getting measured for a pack. I am new to backpacking and I was thinking about taking my older brothers pack (he has a really bulky Kelty pack from the Army). Would this be a bad idea for a first timer?

Also, my first trip was going to be about an 18 mile loop with little to no elevation. I was going to make this trip in about 3 days. I am in fairly good shape and was going to keep my pack around the 30 pound area; does this sound feasible?

Thanks,

Mike

Yeah, don't go over 30 pounds, and that sounds safe and feasible, for a single trip with a borrowed pack if your in good shape. I would get fitted if I was going to buy a pack I want to carry 30 pounds or more on a regular basis, but I don't like to do that anymore anyway. Now I try and keep my total skin-out weight under 30 pounds even on a long trip in winter. That is shoes, everything worn, the pack and everything in it, and all food and water. I step on the scales naked and then I step on the scales fully dressed and I won't go over 30 pounds in winter. 20 pounds for Spring/Fall. Less in summer unless I'm taking my daughter along. I think for 20 pounds, in the pack, I would still make sure a pack fit if I was buying one, but if your in good shape I wouldn't worry about it for a single trip with a borrowed pack. I would reduce the weight as much as I could though. I bought a Jam2, large, and I didn't have it fitted. It just felt right. I can carry 40 pounds in it but I don't. I would guess that when I am carrying 30 pounds skin-out in winter only 23 pounds or so is in the pack. Clothing and stuff will gain weight in winter, but your losing food also, and body fat. lol.

I think if your only carry 20-30 pounds the biggest thing is really your feet and ankles and knees. If you are a typically overweight middle-aged North American, as I am, you want to keep the skin-out weight down. I didn't mention it above but what I really try and do is keep my total weight on the scales, skin-out plus myself, down to 220 pounds. That makes for a really pleasant hike or ski. At my current 230 pounds I would have to go naked and drop a limb, which isn't a real option. 260 pounds ain't bad though. I can still manage to hike and ski 20km a day at that, in comfort, and that's the best way I know to lose the pounds.