How to calculate elliptical calories burned?

Lou2016

I just got a old, used elliptical and it has an option to choose calories burned for your workout. You can choose 300 or 500. I just did 300 and it only took 22 min. I am guessing this is way too high, I don't go that fast and resistance is between 6-7. It also doesn't have you input your weight.

Without buying a hrm, any guesses on accuracy? I was thinking if I just halved whatever it gives me for calories burned I would be good.

Thanks!

sugarandopium

Figured I would bump this up rather than starting a new thread.....

So from what I understand, the machines overestimate by 30 to 50%...

What would be the best way to calculate until I get a heart rate monitor...

Figure on half (this is what I've been doing...... if I used it for an hour, i've been logging in my diary that I was on it for 30mins) ?

Or is there any way to trick the machine into getting a more accurate reading?
Like putting in half my weight and twice my age or something like that??