If you have trained for and completed a half-marathon then you can work out your target time in a number of ways:
- Double your half-marathon time and add 10-15 mins.
- Add 30-45 seconds per mile to your half-marathon pace
- Multiply your half-marathon time by 2.1.
I prefer the last method. Here is an example using the x 2.1 method:
Kelly has a half marathon best of 1hr 45 minutes
Convert this into just minutes: 60 + 45 = 105 minutes
Multiply by 2.1 = 210 + 10.5 = 220.5 minutes
So Kelly could realistically aim to complete the marathon in 3 hours 40.5 mins or 3hours 40 minutes 30 seconds.
To calculate the target pace, go back to the 220.5 minutes version of the target time and divide it by 26.2 to get the target pace per mile. Calculator needed here!
ie. 220.5/26.2 = 8.416 minutes per mile
But what is 0.416 of a minute in seconds?
0.416 x 60 = 25 seconds
So if Kelly can arrive at the start line as well prepared for the marathon as they had been for their half-marathon best performance, then they should be aiming for even 8 minutes 25 second miles. However, the marathon can be a cruel event, and if you agree with the concept of discretion being the better part of valour, then perhaps 8 minutes 30 second miles might be a safer bet for Kelly in the early stages (especially as the numbers are nicer!). This would only equate to two extra minutes over the whole distance, and this could easily be clawed back in the second half of the race if it turned out to be too conservative.