Yet another heart rate/ work out question

EmpressOrange

Hi,
Apologize if this is a bit long.
I'm sort of new to the whole working out thing, but already addicted
I recently started taking heart rate measurements while I'm on my stationary bike (no heart rate monitor yet, just an app on my Iphone, but it's pretty accurate).
I usually work out at a heart rate between155-160
My speed is around 18-19 km/hr with random bursts up to 24 km/hr
I know that's not really fast, but so far that's the only speed I can maintain for 30-40 minutes without stopping.
I'm pretty out of shape, and with that speed and heart rate I have buckets of sweat pouring off me.
MFP calorie count puts me in the "light cycling" category, but to me it definitely doesn't feel moderate lol.
Today one of my cardio activities was 35 minutes of pedaling. MFP put me at 253 calories burned, and an online heart rate/calorie burn calculator put the same exercise at 363 calories burned.
That is a huge difference when you're "eating back" your calories. I don't want to under eat or overeat too much.
Does MFP take your weight into account when calculating your calories?
I'm so freaking confused over this. For 6 weeks I've been working out and eating using the MFP calculations.
I'm aware that when you log in your stuff, it wont be accurate to a tee, and I don't flip out if I go slightly over or under my calories, but with differences in 100's of calories it will add up eventually.
I'm afraid that for 6 weeks I've been eating way less than I'm supposed to already being on a calorie restriction (haha, not counting the last two days when I went a bit overboard with sushi).
Also, should I bump up my speed on the bike and go for less time (can't maintain high speeds for a long time yet)?
Or should I keep going at a slower pace for a longer amount of time as I have been so far?
Thank you so much to whoever answers this.

Mokey41

Go with the lowest number and yes MFP takes your weight into account. Most people over estimate calories burned and under estimate calories eaten so going with the low number helps create a buffer. Even in your exercise was 100 calories a day more it isn't going to create a huge deficit that's doing you any harm.

kmc979

I find MFP grossly overestimates calories burned. say for example my heart rate monitor says I burned 600 calories for the hour I am on the ellipical (which is what I average) when I go to enter it in MFP it is saying something like 850, a HUGE difference. whenever there is a difference (which there always is) I always go with the lower number. Even the machine put my calories burned closer to what my HRM says. I don't trust MFP calorie burn estimate.

EmpressOrange

Thanks guys!
As for working out harder but shorter or slower and longer, which is more beneficial?

Mokey41

Either/or. Depends what your goals are. I go hard for a shorter time because I don't have much time and I want to improve my speed (running is my exercise of choice) but if you only want calorie burn do whichever suits you.

EmpressOrange

Thanks!