Estimating calories burned

ecl265

I exercise on an elliptical for around 60 minutes pretty regularly. When I enter it into the MFP app, it says I've burned 465 calories, but the machine says over 1300. I know there's no way I'm burning 1300 and that machines overestimate. I also know that a heart rate monitor is the best way to determine calories burned, but until I can get a heart rate monitor, is there a way to estimate somewhat accurately how many calories I'm burning? I usually set the machine to a pretty high resistance (around 9 or 10) and the RPM is consistently over 50 for the whole hour. I'm soaked with sweat by the end and feel like 465 calories is a little low. I'm trying to maintain my weight, so having a better idea of how much I need to be eating would be helpful if anyone has any insight. Thanks!