how to calculate your pace for marathon?

Right, I'm prob getting carried away with myself....but, heck, who cares....

I just did 9 minute miles (for the first time ever!) and managed to keep that pace for 45 minutes, and didn't feel out of breath or that tired.

I'm coming back from injury (shin splints) and building up my running again. I was meant to do a half marathon race last week but needed to pull out due to not being able to build up in time to 13 miles again due to the injury. So that was going to be my 'pacer' for the marathon in 6 1/2 weeks time.

My half marathon pace in November 2011 was 2 hours 14.  I was hoping for a 4.30 marathon.

But I had thought my injury put a that out the window.  Since being injured I've been training in the pool (mainly threshold training) and it seems to have made quite a big impact on my speed.

Since the injury I've moved my pace for the marathon from 15 minute miles, to 13 minute miles, I was now thinking I might be able to do 11 - 12 minute miles. But given my run today - could I do it even less?

How do people work it all out????  And any advice would be helpful!

(I'm thinking, really, of doing 11 minute miles, and walking for 1 minute at every mile to drink and re-fuel) Reasonable?

To be brutally honest Kaffeeg, it souonds like you are unprepared to run a marathon in 6 1/2 weeks time. Even if you had built up enough to run the half marathon last week, you'd still be behind in distance as normally you thave a 3 week taper meaning you'd have had 3 weeks left to build up your endurance runs.

Also, as I understand it, 12.45 pace is the threshold at which running any slower is inefficient and uneconomical. Power walking becomes your best option.

Aside from the above, the easiest way to work it out is to base it on previous races of different distances, and this web site's calculator will work it all out for you www.mcmillanrunning.com . I find the results from it a bit optomistic, but it's a decend guide.

Good luck

Just set off and run at 10 minute mile pace

Let us be honest here and say that at some point you will stop running and start walking. 

Let us be even more honest and say that at some point you will stop walking and start crawling (I have been here and started crying, but think you might be tougher than me).

Total shot in the dark but I think you will finish in a time between 5 and 5:30 hours.

You will probably not be able to walk for a month and run for about 6 months.

Sensible advice would be not to do the marathon and build up your running, and one another day. I have at times taken this advice and at other not done so...............one hurts.

use this....

http://www.runnersworld.co.uk/general/rws-training-pace-calculator/1676.html

and/or this....

http://www.runnersworld.co.uk/general/rws-race-time-predictor/1681.html

You need to know your current ability, ideally a race time...or at least a decent and HONEST guess of what you might be capable of....

...and the macmillan thing dibbers mentioned is very good (same sort of thing as the above links)

I don't think running at 12 minute miles rather than say 10 will help at all. 

If you do it then run at a comfortable pace. If you can do 9 minutes for 5 miles then I would think 10 minute miling would allow you to go at a pace you can have a chat. 12 minute miles will probably hurt even more.

Good luck and you won't be the first to do it the hard way!