Calculating climb on a route

I took the new (to me) bike for a short first spin around a loop I did a few times last year. I have not had a workout since Oct 2007. So out of shape, but I don't think I lost all of my base from last year.

This loop was fine today, easier than when I was using my mtn bike of course. It has a few pretty good hills and I went down to my granny gear since I'm so out of shape, but I was ok. It's not as hilly (or as long) as the Danskin Webster tri bike route that I managed to get through last year.

I use mapmyrun.com to figure out mileage and get an idea on speed b/c I don't have a computer, and it will also show you the elevation of your route. How do you figure out that you did a "+xx% grade climb"?
And what's considered a tough grade by normal standards and not just newbie out of shape standards?

The first one is a screen grab of today's route.

The second is a screen grab of Danskin Webster. Is it as hard as they say, or not really? Also, both were loops so why is there an asent and decent for Danskin, but not my local route? I'm sorry if I sound very stupid and I appreciate any insight!

I also did a quick google and will try to figure it out myself, but any insight in layman's terms would be great.
Found this link:

http://www.roberts-1.com/bikehudson/...ness/index.htm

It said: grade = vertical_climb / horizontal_distance

--On Danskin, that big hill looks like you climb about 250 ft over from mile 3 to mile 4.5.
--Each mile is 5280 ft, so that's 7920 ft.
--You take the 250 ft you climbled divided by the 7920 ft to get a grade that's just over 3%?

And that link says:

0% grade is exactly flat (and a negative grade, less then zero, is downhill).

2% grade does not seem very steep, but it's enough to substantially reduce forward speed, and for most riders it will absorb more than half their power output.

6% grade is enough to cut speed to well under half, and absorb more than 80% of a rider's power output (leaving less than 20% to fight air resistance and rolling friction).

10% grade, and anyone who is not a fit and frequent rider is off their bike walking -- and anyone who is not a racer is reaching for all the extra power they've got.

So 3% was a decent grade, but no big deal for normal, fit cyclists, right?

Yes!