Only guesstimate I have ever seen is take your 1/2 time x 2, then add 1 hour. For example, 5 hr 1/2 x 2 = 10 hr + 1 hr = 11 hr est. finish time.

worked for one of my three IM's for what it is worth

This formula is probably as good as any, but keep in mind that an IM is a completely different race than a 1/2 IM for all but the strongest athletes. If the last half of the marathon is just a death march (like mine), then no formula will work well.

I think you would be better off finding where you placed relative to your age group in the half IM, then look at how that age group did in your intended IM. Take that time and start working your time up from there. Ask yourself if you will run out of gas and factor in from there.

The last 6 miles were a death march for me. went through half way in 2 flat, held through the aid station at 20 and then I just lost it.

2 hours for the half, a little over three for the 20 and a 5 hour finish time.

Stand alone half 1.25......

Two, halves, do not make a whole.

I've found the following "rules of thumb" work pretty well...

1/2 IM x 2 plus 40 minutes (1/2 IM = 5:00, Then IM = 10:40)

OR....Wildflower Long Course x 2...This has proven the most accurate for me and my friends if your IM is IMUSA or IMC.

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http://wattieink.com/elite-team/
Raising funds to help wounded veterans and racing RAAM 2013 with http://team4mil.org/
"If you are gonna charge... CHARGE HARD!"

just kinda curious. if u did both wildflower and imUSA could u compare the bike courses for me. i've done wildflower before and will do it again this year but my wife also signed me up for imUSA and i'm flipflopping on that one.

Do 2 half Ironmans back to back and add the time together.

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Tom Demerly
The Tri Shop.com

Or do a double IM. 1/2 that time minus between 4 and 6 hours would be about right!

2 times the half plus 3 friggin hours death marching through run miles 10-26.

Worked for me. :-(

You speak the truth.

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Tom Demerly
The Tri Shop.com

I am proud to say that I ran the last 6 miles in WI in 1 minute less than I ran the first 13.1 and 1 hour exactly more than I ran 13.1 through 20.

The really funny thing is as well is that you cant explain this to anyone but there was nothing wrong with me, I just did not want to run, I started walking and could not stop.

I knew I wanted to run, I knew I could have run, even prehaps should have run but I could not do it.

Mind you I think part of it may have been nutrition related as I dont think I was entirely playing with a full deck those last 6.

I just did my first 1/2 Iron in 5:07 and I ran 1:45 ( without transition time 2min... ) for the 1/2 marathon feeling strangely strong on the run after struggling in the last 30 km of the bike.....

I ´m planning to do the Ironman Brazil next year in May and I´m expecting something below 11 hours..... Based on the experience that you guys shared with me and a lot of training I think is pretty much possible.....

Next month I will run my first Marathon...

Thanks for all replies....

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Luiz Eng

So Julian, what are you up to this year to make the death march at IM Lake Placid a bit shorter? You will be there, won't you?

I only ran the first 6 miles non stop last year. I am hoping to make it to the half marathon mark this year before the death march starts. I have been running more this year, but I just can't get more than about a half marathon of running into these old legs.

I know I could do a half IM under 6, but 13 hours would be a great time for me in LP. It will take some good fortune to hit that mark.

AJ, how fast do you bike?

I did a 40K time trial on an extemely fast course last year at 22.5 mph. I would have done IM Lake Placid course last year in 6:40 had I kept air in my tires. I am over 40, over weight and out of shape, so those hills kill me. I do an Olymipic distance trialthlon bike leg at 20 mph.

For all but the real studs, I think your speed in the latter stages of an IM has more to do with how well your stomach sucked down food and water during the day than any of the above formulas. Having a smooth running style like I had 25 years ago must help too.

It is a long day out there. Try to stay patient.

About the same, went 1.15 at an Oly last year, 1.09 at Mrs T's which is flat.

7 hours at WI, I could have gone faster and for what its worth in hindsight might as well have done so that I could get to the walking part faster. :)

I did run the first 20 at WI at 9.00's though.

Running the first 20 at 9:00/mile is just terrific. You are almost there. I am going to guess that a little more energy into drinking and eating and a little less into running fast, and you are if fat city.