Calories - how accurate is it?

Independent of any device, accurately measuring calories burned while swimming is difficult to do. Coming up with an algorithm that estimates how many you burned is likewise very difficult. Considering that the Garmin Swim device has only two parameters to work with -- distance and time -- it's safe to say that the number of calories burned is just an estimate.

Thank you!

I understand that it is sort of a formula distance-time-weight and without heart rate during the session and perhaps age it is impossible to get an accurate number.

Since the number is quite large :)
I am wondering about the error margin for this 5%? 10%? 30%?

Here is a link to the FAQ about calorie computation: https://support.garmin.com/support/searchSupport/case.faces?caseId={6304f3e0-fad2-11e0-73d0-000000000000}
What's been posted already is pretty accurate. The calculations do also take into account stroke type that was used.

I see consistent underestimates, am I doing something wrong?

Hi,
In my last session, the watch showed for 75min swim (81min + rests), 4000M distance, 1016 calories.
assuming I have the correct weight update in the watch, how reliable is this number?

Thanks
Guy

Interesting, I just completed a 74 minute swim (80 mins + rests), 3600M distance (sorry I am slower than you!), and it only registered 593Kcal. Most estimates I have seen would indicate that more like 1000Kcal would be a better estimate. I checked and my weight (175lbs) was correct. Any thoughts? Are there other settings?

Brad

indeed it looks low. is it like that in all swims?
my weight is 184lbs so I guess my number should be a bit higher, but not almost twice.

593Kcal is too few i think. Yesterday i did a 74 minutes (no rest) open water swim using a 910xt (i suppose the algorithm used by Garmin in both devices is the same), so the 910xt indicated 4630m (it was a bit more indeed) and 1516 C. Weight 90kg (198lb). It is always around those numbers. So too much cals in my case or too few in yours?

http://connect.garmin.com/activity/257914947

593Kcal is too few i think. Yesterday i did a 74 minutes (no rest) open water swim using a 910xt (i suppose the algorithm used by Garmin in both devices is the same), so the 910xt indicated 4630m (it was a bit more indeed) and 1516 C. Weight 90kg (198lb). It is always around those numbers. So too much cals in my case or too few in yours?

http://connect.garmin.com/activity/257914947

Open water calorie computation is a bit different because stroke type is not known so the Calorie algorithm assumes freestyles (likely a safe assumption in most cases). Otherwise you are correct that it is the same algorithm in the 910 and the Garmin Swim.

Posting the GC links to the workouts where there are questions about the Calorie computations would be helpful.

Here are a couple of examples:

http://connect.garmin.com/activity/260866856

http://connect.garmin.com/activity/254995394

I do use the Drill function, is calorie consumption assumed to be zero during Drill activities? Although I am not sure that even that would explain the discrepancy.

I have the same problem i swim one hour 2400m different styles ..i am a medioum swimmer i would say ...43 swolf...and it shows only 251 calories ..i think its way too low...i am 51 kilos

Are you doing drills? I don't think drill logging counts toward your total calories.