tbox
with respect to my colleagues;
You can't compare. We don't know where you are going, what the conditions are, what the chances are of the mud hitting the fan, or your level of experience. Most of the people responding have a great deal of experience and are comfortable having expertise stand in for equipment.

If you are at 21 pounds that's good enough. Go use your gear and determine what you can leave out, and what you left out. After using that pack and gear a bunch of times you will have a better idea how much volume you need in your pack and then you might find a lighter smaller or larger pack as suits your needs. Don't let a number cloud your judgment, 21 pounds isn't a lot and would be considered lightweight few years a go. I generally carry 21 to 28 pounds all year round, 21 summer, 28 winter, in between for the in between. What ever you do, do not leave out warm clothes and insulation in the interest of weight unless its 80 degrees at night where you go. Repeat - never leave out what you think you will need in the interest of having a pack as light as someone elses. And do use a spread sheet.
Jim