Holy different readings batman!

Take an average of the three?

Caloric burn is not tied exclusively to intensity. Doing high intensity cardio for shorter durations is much better for your weight loss, even if the "burn" is less than lower intensity for longer periods (like walking). The harder you make your body work and the longer it takes your body to recover, the more long-term benefits you will see. You will get more "after burn" from high intensity workouts.

It is pretty well established on here that MFP and machines like treadmills grossly overestimate your burn. I would consider a good heart rate monitor to be vastly superior and I would go with that number.

In my admittedly limited testing, I've noticed that wrist HRMs (with no chest band) tend to be inaccurate. In my case, they've tended to way overestimate the calories burned, but I can see where they might underestimate as well. Anything that relies on pulse readings in the fingers seems to be off on calories burned, including treadmills and ellipticals (though the heart rate is usually correct).

My Polar FT7 has been much more accurate, I've felt. If you tend to walk or use treadmills a lot, I would also recommend using something like a Fitbit (I love mine). Though it's not a HRM, the estimated calories burned are much closer to my chest HRM than wrist HRMs or the HRMs on equipment.

Just tested out my Mio Motion on my treadmill fast walk / run. I was running at a 5 yesterday but when I checked my heart rate on my Mio it was too high so I knocked it down to a 4.5. So heres my dilemma... my Mio says I burned 139 cal for 30 minutes (13:08 at 4.5 the rest at 3.5)!!! That seems super low to me. My Runtastic program worked today and put me at 368 and my treadmill which has no height or weight info had me at about 280. What would you guys do with this info? What calculation do I use?

Hard to say without knowing your weight. For what it's worth, I walk a lot with my HRM, I'm 180 lbs, and for 40 minutes at 3.5-3.8mph I burn 200 calories. 30 minutes has been anywhere from 130 to 180 calories. Seems to me neither of those are accurate. What does MFP say? I've found it's usually pretty close actually. I'd enter 4mph for 30 minutes and call it a day.

From my experience, I've found a few notable things about calorie burn:
- The amounts on MFP are seldom even close to what an exercise machine or a HRM shows.
- Exercise equipment (treadmill or elliptical) will record a higher calorie burn at lower exertion (less than 135 bpm) than I get with a HRM.
- The HRM will record a hire calorie burn at higher exertion (greater than 145 bpm) than I get from the exercise equipment.
- When I compare my general fatigue after a workout, it correlates best with recordings from my HRM.

Given all of the above, I take my HRM and subtract 100 calories per hour (assuming I'd have already burned 100 calories sitting still that hour as a part of my basic metabolism).

I weigh 194 (down from 279) and I'm 5'1" tall. I guess if I just eat the 1200 calories suggested by MFP and don't eat back any calories burned, I should be ok. Although we go out drinking once a week and I liked using my burned calories on that day.

It just doesn't make sense to me that I walked (fairly slow pace) for 27 minutes and burned 114 calories but I ran & fast walked (3.5-4.5) for 30 minutes and only burned an extra 15 calories.

I would suggest eating the workout calories back because your body needs fuel to keep your fat loss going, especially after a workout. Also many will talk about your body going into "starvation mode" if you eat too few calories and/or don't eat back your exercise stuffs.

MFP and machines will only give you estimates based on your weight and not your actual heartrate, I usually underestimate them. If you want really accurate readings get a heart rate monitor for when you walk and run, they will make the biggest difference.