Hill Walking Calories?

I recently bought a heart rate monitor that also shows calories burned (Polar F4). I'm having fun doing various activities and seeing the burn it shows as motivation to push harder in my workouts. Today I went for a 50 minute walk in a very hilly area and was surprised to see that it showed 330 calories burned. I was going at a good pace and there were some steep grades, but that's still much higher than I expected. Does that seem right, or is the monitor probably overestimating?

Oh, and if it helps I'm 5'10" and 172 lbs.

From my experience that seems about right for your weight.

I have the same HRM and I'd agree that that sounds about right.

Ok, thanks!  I just wanted to see if that sounded accurate since I'm using the HRM readings from my workouts to gauge my deficit/how much I should be eating. 

I do hilly walks as my main exercise, and give myself 500 calories for a 1.5 hour workout, so that sounds about right.

 Hills are a calorie burner allright - you're lifting your whole bodyweight higher with each step, and that takes a lot of energy ;)