flat to climbing mile times

10,000 ft?

Pray.

And don't forget your mountaineering gear.

How fast do you walk?

Seriously.  If this is your first half and you haven't trained on hills, it's almost guaranteed that you will be walking A LOT in a half with that much climbing.

To answer you more generally:  There might not be that much difference in overall time, if the net elevation change is near zero...in other words, if there is a downhill to make up for every uphill.  On the couple very hilly HMs I've done (which started and finished close to the same elevation), my time wasn't far off my typical time for a flat course (and still faster than my HIM run splits, for that matter).  OTOH, if it's +10,000' of net elevation change (i.e., if this is a run up a mountain), then all bets are off.

This has to be a typo...I'm guessing 1,000 feet?

I don't think there is a road on this planet that gains 10k feet in 13.1 miles.

There are organized trail events around here that fit the bill...the run up Mt. Baldy is about 10,000' of gain in 12 miles, I believe.

Small rollers might not affect your overall time...but climbing steep hills will.  You can't simply make up the amount of time lost.  If so...people wouldn't be looking for flat courses to BQ on.

If there exists course that has a hill so steep (maybe 20%) that I have to walk up the first 6.65 miles at a 20:00 pace...that will take me over 2 hours.  I'd have to run the downhill so fast that I would have to travel back in time to come close to my 1:41 HM PR.

I agree that this has to be a typo, because for example the Mt. Evans Ascent, which is considered one of the toughest uphill shorter distance races gains about 4,000 ft in 14 miles or so.

My recommendation would be to find a treadmill and practice pacing at different slopes.  1000 feet of climbing is relatively a lot for a HM.  Expect your avg pace to be significantly (30 sec/mile? just a guess) slower, esp if its your first time running this distance.

Does the "road" go up that much?  I'd imagine there would be a lot of switchbacks that would lengthen the route, and decrease the grade. 

Good advice here.

Double dipsea is about 4000ft

Round-Trip Length:13.7 milesStart-End Elevation:132' - 88' (1,370' max elevation)Elevation Change:-44' net elevation loss (+4,112' total roundtrip elevation gain)

quad is 9000 and 26+ miles

To answer your original question, no, I don't think there's a good formula to compare flat miles to what you are about to do... it's just too different.

When you say "try" a half marathon, does this mean that you haven't ran one before (flat or not)?

Usually with elevation changes, what's meant is the amount of ascending. Not the combined ascending and descending. How much of that is there?

I'm not sure of a good conversion. It's rather dependent on the individual's ability, size and the terrain. "Quite noticeably slower" will have to suffice.

And Pike's Peak half marathon (and full) do get up near 10,000. I think it's like 8,000 or so.