Logging 5K's

WeepingAngel81

I am running in the Dirty Girl Mud Run this weekend which is similar to the tough mudder, just on a much smaller scale. There are obsitcals with running between each course. I ran another 5k earlier this year which was easy to log in my exercise journal since it was straight running (or in my case jogging). I know that without a HRM I won't get an accurate calorie count, however, what is the best way for me to go about logging this 5k into my journal without the use of an HRM? I have one, but I don't want to wear it during the run. I have also checked in the database and maybe I wasn't typing the correct word combo but I couldn't find anything similar to 5k mud run.