Swim: 1,000 m/110,645 m
Bike: 0/1,247.9 miles
Run: 5/494.5 miles
I’ve been training for my half-marathon with specific paces set by my training plan. Those paces were based off a predicted 20:40 5k time, which, in turn, was extrapolated from the 43:12 10k I ran in April (a PR). This past weekend, after I blew the doors off that predicted 5k time with a 19:12, I thought it would be entertaining to plug my new time into the McMillan Running calculator to see what my predicted times for other distances might be. If nothing else, the results were good for a laugh:
A 39:53 10k? I have no doubt that I could set a 10k PR now – I do it almost weekly on my tempo runs - but shaving more than 3 minutes from my best time and running a 6:24 pace? Seems like a stretch.
A 1:28 half-marathon?? My training runs this season have put me in the 1:33 range.
A 3:07 marathon??? That would give me a BQ – by the newer, tougher qualifying standards released this year – by almost 3 minutes. (It would also be a marathon PR for me by exactly one hour.)
Of course, when you start with a much shorter distance and extrapolate upward, those performances at the higher end become highly theoretical. They would only be a result of intense training - just running a quick 5k doesn’t mean I should purchase my plane tickets to Boston quite yet. But maybe, just maybe, there’s some kernel of truth to the math behind these predictions? Perhaps so, but I don’t necessarily believe that running a fast 5k guarantees that I could hit that marathon time no matter how much I train. Sometimes a body just isn’t built to hold that pace for so long.
In any case, it’s fun to dream. And now I have McMillan to back me up!


I think you’d be surprised at what you could do. I’m not a huge fan of the race predictor, but McMillan has been pretty spot on with plugging in my PRs and what has actually happened.