MP

I would base it on my walking time on a fairly level wooded (not Path) walk.
So at 2.69 miles that =  170438.4 inches.  My stride is 27 inches, divide that into the 170438.4 = 6312.5333 steps.  Now for the grade factor I would cut my stride by .33 ( less 8.91 inches) for grades 5% to 10% that would make my stride at 18.09 inches Any grade over 10%  I would cut it by .66 ( less 17.82 inches), that would be 9.18 inches per step.  At a 5-10% grade you’ll still be walking pretty much in a straight line. Over 10% going uphill or down I suspect you will be making much shorter steps or walking from side to side.  I figure my steps usually 1 per second so at a level grade it would take me about 1.7534815 hours to walk it.
Now take into account the grade changes from typo maps.  Figure the percentages of different grades and you should be pretty close.   This is a figure I use hiking in the Gorge and the only things that really throw it into a default are mud, water, pictures, and snack breaks.   Don’t take a camera or snacks and you’ve already cut that default by 50%. ;)

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