Pacing / Split times on undulating courses

Does anyone know of a website that can make sensible estimates of mileage split times, taking account of the undulations on a race course? 

Obviously, you can already map out a route, and software will show you the undulation profile...   it would not be a big technical leap for this to be translated to split times adjusted to take account of these undulations.

I'm doing my first marathon, and am over-ambitiously planning for 9:09 per mile  -  but, for example, the last mile is a bit up hill.... so need to have something in the bank! 

I will do some split time planning manually - but just wondered if there's an easy way for me to be lazy!

I don't know a rule that explicitly states how much time you lose on pace for every metre of ascent/ descent. But this marathon pace calculator does allow you to factor in fade from a specified point in the marathon course.  By experience, I would suggest that after 20 miles you might want to see what a 10-15% fade in pace would do to your timing, running as a mara newbie.

Good luck.

I don't think it matters how clever your algorithm might be, there's no way you can accurately account for undulations, because people react differently to hills, with some people being better hill runners than others, not to mention people being relatively better at running uphill than downhill, etc.  (It's a fairly predictable pattern of mine to overtake people running uphill on cross-country courses only for them to catch me up again going downhill.  Maybe I'm not brave enough...)

Forget all that and run according to even effort. 

Thanks Tricky Dicky...  that tool is simple and straightforward. I like it.  I've input the figures you suggest - gives me 8-55 for the first 20 miles  - Then 10-10 after that. There is one main downhill and uphill... so I'll use just make a minor adjustment for those.

The times are a step up from where I am now (currently doing 9.00 for 13-14 miles then fading quite a bit)...  But that's running alone, against my Garmin!  I have to hope the adrenalin and encouragement of the day sees me through!

Thanks for the advice too.   I'd wondered if you could have an algorithm that had some default settings, but also allowed the user to input some variables to account for how well/badly that an individual takes hills.  It won't be perfect, but I think could prove useful