My fitbit Surge doesn't track indoor cycling calories accurately

[Pauis]

I bought my fitbit Surge in february 2016 and I was wondering why my fitbit is significantly underestimating the amount of calories when using my indoor bike (i.e. The bike reads 400 calories while the fitbit only reads about 180). And before you mention that again, yes, I have already checked the position of the watch and the dominant hand. Now, mine is a surge and I have been investigating and you guys state in your website that the surge and blaze CAN track cycling, not the other ones though, but like I said, mine IS a Surge so ... What I am missing here? See here were I found the info: https://help.fitbit.com/articles/en_US/Help_article/Does-the-Fitbit-tracker-accurately-track-calorie...

[scolbour]

I use my Surge when riding exercise bike and attach it to my ankle. the calories correlate well it adds steps to my daily log 1 per revolution of the pedal but the distance is low for 10km on the bike I get 2 km on the Surge

[MikeF]

Which mechanism are you using to track the indoor biking? I assume that it's the 'Spinning' exercise mode but since you don't mention it, it's probably better to clarify than guess.

[Pauis]

Correct! Spinning!

[bbarrera]

One guess is that the Surge is failing to accurately read your HR. Problems with HR accuracy is a relatively common issue with spinning and Surge.

Manual logging is also off, for example I'm just over 200 pounds and I usually burn 800-1200 calories per hour while spinning at 80-90% maxHR. Fitbit finally added a new manual spinning entry, where you can enter miles which is an indicator of effort, however the new spinning entry is worse than the old one that just used time and weight to estimate calories:

The minor calorie differences between Jan and today are due to my weight being up a few pounds.

[scolbour]

Ah I was actually using the treadmill mode I was not sure what teh spinning mode was for I'll try that see what happends