Predicting Your Anticipated Marathon Time Based on Other Races

Have been running regularly through the holidays, though nothing too long, speedy or intense. Generally 30 to 45 minutes per day. Would love to kick it up a few notches but the holidays and year-end crazyness make that a challenge.

After a visit to the eye doctor the other week, my spring marathon plans may be a bit up in the air. Since the vision in the right eye is terrible and not correctable with lenses, I will be doing another eye surgery next year, quite possible in the January/February time frame. If I can get my running mojo back and ramp up to 20 milers by late January, it's possible to run a decent marathon.

Speaking of marathoning, a topic of interest to most marathoners is how to predict your marathon time based on your times in other distances. Over the years I've used rules of thumb to predict my time, such as multiplying my 10K time by 4.7 and multiplying my half marathon time by 2.1. The resulting total is my predicted marathon time, assuming I've done sufficient long distance training.

To use these formulas, you have to convert from hour/minute format to total minutes in decimal format, then after doing the calculation convert the resulting number back into hours/minutes.

For example: If I've recently run a 38 minute, 25 second 10K, to predict my marathon time, first I convert the 38:25 into decimal format. To convert 25 seconds into minutes, divide it by 60 seconds and the result is .42. Then add .42 back to 38 and you get 38.42. Multiply 38.42 by 4.7 and your marathon time is 180.57 minutes.  Now time to convert .57 back into seconds by multiplying by 60. That equals 34 seconds. Add that back to 180 and you're running a 180 minute (3 hour), 34 second marathon.

OK, that's a bit technical, so I have a better solution. Visit and try the great running calculator that calculates all sorts of projected race times based on a range of actual times. Typing in a 38:25 10K into this calculator generates a predicted marathon time of 3 hours, 17 seconds.  Pretty darn close to the rule of thumb.

Check it out! It's simple, quick and great!