As stated on another page, if you are new to running, this might mean 6 months to build up to the sort of distance that you need
to be confident of running your first marathon.
Don't panic if you have less, but do plan carefully how you build up the mileage.
At Momentum Sports we believe in two additional elements to the Long Run
1 - Take a lighter week every 4-6 weeks, where you run maybe half the distance you have built up to.
2 - Do some of these runs as races. This will allow you to learn your comfortable racing speed and learn all about what the races
involve. So, you might look for a 10k after 6 weeks training, a half marathon 3 months before the big day and a 15-20 mile race
about 6 weeks beforehand.
We don't like to specify exactly what distances you should be running for these sessions as it is a totally individual thing, and
will depend on your fitness at the start, how you progress as you go along, the amount of time before the race day etc etc.
However,
using the guidelines here, you can make a good start on building a plan that will work for you.