Guestimate your Marathon Finish Time

Most of us do some of our marathon training at a pace based on our anticipated marathon pace. Even if you are a frequent marathoner, that time lighting up as you cross the finish line can vary. I’ve been exploring how to best determine my likely finish time based on a number of calculators available online.

Most of the calculators assume that I have done adequate training The Runsmart Project used the Jack Daniels V-Dot calculator. Based on my recent 10K race time, calculated finish time is: 4:32:15 (pace 10:23). Then, I used my 1/2 marathon time also done in the last two months; Calculated finish time: 4:44:03, (pace 10:34).

The Fivethirtyeight Project factors in mileage during marathon training and allows for difficulty level of recent races. So I chose my 10K which was a beautiful, cool, although slightly windy race on a flat course. My second choice was my recent 1/2 marathon held on a course with some hills and uncomfortably warm temperatures. The result was a calculated marathon time of 5:00:15.

Runner’s World allows for input on two recent races (I again used my most recent 1/2 marathon and 10K times). It also asks for usual weekly mileage. My calculated finish time: 5:03:55.

Sporttracks calculates finish time based on last 5K time and the assumption that my pace will slow later in the marathon. My calculated finish time at 5:33 (pace 11:33). Ouch! That’s a long time to be on the course.

Finally, a newer calculator that can be found on the FetchEveryone site. It seems to lean more to the recreational runner, using training times from runners who have posted their training on the site. I input my half marathon time to generate a result for females of 5:20:46.

Most of the race calculators address the fact that their calculations are more spot-on for elite runners than for those of us running under a 4:00 hour marathon. The FetchEveryone calculator is the only one that provides a different outcome for men than for women.

Looking at this collection of calculators, they span almost an hour in finish times. While I would love to see a 4:32 time at the finish, that is indeed optimistic. The 5:33 time at the other end of the spectrum is disheartening, but perhaps more realistic.

Any way you calculate it, once the training is done, I’ve found that so much depends on my health on race day, on the weather and on the condition and difficulty of the course itself.

Based on my recent 10K and 1/2 times, what is your guess for my next marathon finish? Do you look at race calculators to adjust training? How close have they been for you?


  1. This is quite fascinating. It has been a full 6 years since I have run a road marathon. I remember at the expo there I picked up a chart about the size of a playing card with various 21k times and then the estimated marathon time. The 10k wasn’t on the chart. It was actually quite accurate. I was only 2 minutes faster than the chart. It was a good day for me. So with that in mind, my guess for your marathon would be 4:42. Trail marathons and ultras would be so hard to guess, because each race is so different. 😀🏃‍♀️

  2. Carl, I will be writing more on this net week. I found it interesting the different factors some of the sites used to make their determination. Like you, it has been a couple of years since I ran a road marathon. Finally scheduled one this month and I hope to get one or two in this coming year.

  3. I tend not to look at calculators and guess based on feeling…. I was roughly right for a ‘non-race’ marathon I made last August (racing has not been happening in Thailand) but haven’t actually ever done a marathon race, so I guess we will see sometime! I will try all those calculators to see though

  4. Happy New Year Mary Lou and May it be a healthy one for you and yours.
    Thank you for your support in 2021.
    I still haven’t taken up running and sadly my walking practice has reduced.
    Left hip pain initially caused problems, inclement weather and more recently constant rain and ‘shin splints’ of all things.
    I have discovered the condition has arisen by wearing I’ll fitting indoor footwear with my custom made shoe orthotics. I have ordered a pair of good supporting indoor/outdoor slippers which arrive 8th January.
    Small steps! (Excuse the pun)

  5. Margaret, a happy healthy new year to you as well. Yes, the right footwear is so important. I go to a store that sells nothing but shoes for running and walking. I recently saw an article on Sixty & Me about taking up running after 60. I don’t recall the name of the author. I thought it was well written and likely helpful fort anyone starting out.

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