Predictions!

I have been fascinated with running times predictions, i.e., predicting your time in one race, based on times in other races, ever since I read a 1977 book by Manfred Steffny "Marathoning" (see previous blog). From Manfred’s book I first read about the possibility of predicting your marathon time, based on your 10K time. He gives a very simple formula:

Marathon time = 10K time x 4.666 (1)
He later modified to: 10K in 30 minutes -> Marathon in 2:20. For every extra minute in 10K, add 5 minutes to the marathon (2)
A more conservative estimate (recommended for beginners) is even more simple: Marathon Time = 10K time x 5 (3).

Right now my 10K PR is 41:20 (2007). My best marathon time is 3:22 (2009).

(1) 41:20 x 4.666 = 3:13
(2) 2:20 + 5x(41:20 – 30) = 2:20 + 56:30 = 3:16:30
(3) 41:20 x 5 = 3:26:30

Seems like my actual time is between (2) and (3). I think formula (3) is more typical for people without enough marathon experience/training and it is very easy to remember: Formula (1) might be my upper limit and (2) something to aim for.

Here is a table published in Manfred Steffny’s book:

Max. possible Realistic
10Km marathon time marathon time
------ ------------- -------------
27:00 2:05:00 2:08:30
28:00 2:10:00 2:14:00
29:00 2:15:00 2:19:30
30:00 2:20:00 2:25:00
31:00 2:25:00 2:30:30
32:00 2:30:00 2:36:00
33:00 2:35:00 2:43:00
34:00 2:40:00 2:49:00
35:00 2:45:00 2:55:00
36:00 2:50:00 3:00:00
37:00 2:55:00 3:07:00
38:00 3:00:00 3:15:00
39:00 3:05:00 3:20:00
40:00 3:10:00 3:25:00
42:30 3:22:00 3:42:30
45:00 3:35:00 4:00:00
47:30 3:47:30 4:20:00
50:00 4:00:00 4:40:00

The Realist time is more appropriate for someone’s first marathons. The Table stops at 50min. Older runners and women can use the formulas.

I have devised two more simple formulas to predict marathon times from 10mile and ½ Marathon times:

(4) Marathon = (10 mile time) x 3
(5) Marathon = (1/2 Marathon) x 2 + 15 minutes

(4) My 10mile PR is 1:08:31 (2007) x 3 = 3:25:33
(5) My ½ Marathon PR is 1:32:50 (2008) x 2 + 15min = 3:20:40

Both are reasonable.

But the mother of all prediction calculators in the internet is here:
http://www.runningforfitness.org/calc/rp.php

You enter your age, gender, and one race time and it gives you several predictors, plus an average prediction. Cool! But there is more in this web site... It will also calculate how weight loss will affect your running times and more.

Staying on the topic of Marathon time predictions, I tried this web site and here is what I get:

Distance PR ----------- Predicted Marathon
5K – 20:06 -------------------- 3:10:33 - 3:25:57
10K – 41:20 ------------------ 3:10:11 – 3:24:52
10 miles – 1:08:31 ---------- 3:10:35 – 3:23:29
½ Marathon = 1:32:50 ----- 3:13:57 – 3:25:09

The first marathon predicted time is an average of several formulas. The 2nd time is called the “Purdy Formula” and it seems more realistic to me. To read more about these formulas, go to the link above.