Calories burned in a 'body pump' class

Hi,

I am planning on doing this body punp class later and i am just wondering how to add it to my diary as i dont have a heart rate monitor, any ideas what i should fill it out as? I am 5ft 1' 21 yrs old and moderately fit.

Body Pump:
A cool way to work out to music whilst weight training using a barbell and step. If you want to tone your body like never before but can’t seem to get the results by yourself, this class is for you.