You're entering the transition area of an ironman triathlon, after finishing the swim and bike legs of the race. With 26.2 miles to run, and typically with wobbly legs after riding 112 miles on the bike, as you're changing into running shoes, it's natural to wonder: how long is it going to take me to run the marathon? What will my finish time be?
At this year's Ironman Wisconsin, more than 2200 athletes were possibly thinking the same thing. After analyzing the results of all finishers, the answer is as simple as this: the average marathon was equal to swim + bike time multiplied by 0.6.
If you start your marathon with 7 hours elapsed in your race, your marathon target should be 7 hours x 0.6 = 4.2 hours = 4 hours, 12 minutes. (remember, the .2 = 20% of an hour, or 12 minutes in this example).