Predicting a marathon time is not straightforward, as it depends on numerous factors, including your training, experience, health, age, race conditions, and other variables. However, here you’ll find some general methods to predict your marathon time.

American Engineer and marathon runner Pete Riegel conducted some research and created a formula that has become somewhat of a standard for calculating race times. It has been widely used for over 20 years and stood the test of time.

The formula is:

T2 = T1 x ( D2 / D1 )1.06

Where:
T1 = Time for a known event
D1 = the distance for a known event
D2 = the distance to predict a time for
T2 = the forecast time for D2.

As an example, if you have recently run 5km in 25 minutes and you wanted to calculate your likely 10km time, this would be the formula:

25 x ( 10 / 5 ) ^1.06 = 52:07

There are a few assumptions Pete Riegel’s formula makes:

• It presumes you have done the right level of training. ie. a 5km runner won’t get a good result for a marathon if they haven’t put in the relevant training
• It presumes you don’t have a natural gift for one type of race (speed or endurance)
• It is only applicable for races within 5 mins to 4 hours.

This formula is more skewed towards experienced runners than those attempting a race for the first time, so bear that in mind. Obviously, there will also be other variables such as the weather, terrain, and how well-prepared or recovered you are, but at least this gives you a good starting point.

Yasso 800’s

Another method you should consider when predicting your marathon times are Yasso 800’s. Yasso 800’s are a popular track workout created by Bart Yasso, the former chief running officer at Runner’s World magazine. The theory behind the workout is that running 10 x 800m intervals with a short recovery run in between will gauge whether you can run a marathon at that target pace.

How to run Yasso 800’s:

First, calculate your target time. If your goal marathon time is 4 hours, you should run each rep in 4 minutes. If it’s 3 hours 30, run your reps at 3:30.

• First warm-up
• Run an 800m interval at your target time
• Do an easy recovery run within the same target time
• Repeat 9 times
• Cool down and stretch

Note this is a pretty challenging workout. The first time you attempt this, you may want to reduce the number of reps to 3 or 4 and slowly work up to 10 reps.

Hopefully, some of the techniques above will help you predict your marathon time.