While obviously not the same as what is actually burnt, how reliable are they in general? For those of you who properly train with them, do you have a rule of thumb for how much you knock off? If I ate as much as I appear to burn off, the result would not be good!

Half them and you’ll be getting close.

depends on what Garmin you are using

Have a read here

http://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html

I have an Edge 200 and shorter rides with a ****load of climbing are coming out only proportional in mileage terms, so this makes sense:
“This speed/distance algorithm does not consider or evaluate the impact of elevation change – primarily due to concerns the team had about relying on GPS-based elevation to determine calories.”

The page still reckons “65-80% accurate” and even this seems quite high. @scotroutes – anything beyond anecdotal evidence?

short answer = just over half.

On my logged road rides my edge 500 typically records something like 1000 calories per hour. Based on years of polar hrm use that figure seems a bit high so I tend to think it’s closer to 500-600 p/hour.

Of course I have nothing to say that the polar is any more or less accurate other than i think that if I got back after every Sundays ride and ate the 5000 calories that the garmin thinks I’ve expended then I would be a super whopper.

if I got back after every Sundays ride and ate the 5000 calories that the garmin thinks I’ve expended then I would be a super whopper.

My thoughts too, about me, not you. 🙂

Just use it as a guide to how hard i’ve worked on a long ride and the excuse for a curry afterwards.

Fiction, imo. Impossible to tell from the information they have I reckon.

I’ve used Polar HRM’s for years and their calorie counts *seem* more accurate. There was a tale a few years ago that Garmin wanted to licence Polar’s algorithm but couldn’t/wouldn’t due to cost.

I fiddled with the weight value in my 705 until calories counted are roughly the same as my Polar.

I fiddled with the weight value in my 705 until calories counted are roughly the same as my Polar.

Cunning like a fox.

Half them and you’ll be getting close.

I use an edge 500 with hrm. My 20 mile commute takes 70 minutes on average and I record between 500 and 600 calories pretty much every ride (unless its blowing a gale and it takes me a lot longer). I reckon this must be pretty accurate as there’s no way I burn only 300 calories on a brisk 20 mile ride.

Just done a little test of sorts.

Just completed 90 minutes on the turbo, 30km avg. The garmin edge 500 and chest strap measured this as 1008 calories. Which I think works out at about 672 calories per hour. Which I guess is a little high but not ridiculously so.

Sundays lumpy road ride which was a lower average speed but ridden without chest strap so i assume this must be a different calculation method works out at something around 1040 calories per hour.

That’s quite a big difference and I was definitely working harder on the turbo than during what was a fairly relaxed social ride. Looks like wearing the HRM is what makes the big difference in accuracy.

If it’s got your weight, heart rate and distance covered, it should be pretty close shoukdnt it? Okay, there will be personal variance but if it’s not counting the weight of the bike or the hills, surely it would under estimate your calories. I did a century last weekend with over 8000 ft of climbing. Polar hrm said that was worth 5500 kcal. I’m tempted to believe it.

Garmin with HR ~1000 kcals per hr.

Powertap ~500-700 kcals/hr.

The powertap gives an exact calorie reading based upon work done. 500 would be a relatively easy ride(with a few lumps and a few efforts). 700 is proper trying(TT pace)

What do you reckon then per mile of road biking at ‘moderate’ pace?

My running Garmin says about 100 calories for running a mile, which I’d always believed (for lack of any other evidence)

Too many variable factors, stick with 500-700 per hour.

Given they appeal to people who like to see big numbers to convince themselves they’re losing weight, I’d expect there is be an upward trend with manufacturers vying to give the highest number.

Personally I would consider them to be pretty much a work of fiction.

between 350-450 for my commute – a 20km route with 250m climbing at moderate pace and taking 45-50 mins, measured on an edge 510 with HRM

seems about right

30 Calories a mile. More if windy/pushing it, less if pootling. Double if racing. It’s not far off my Power meter reading.

My Garmin Edge 305 gives 90-95% of the calories compared to my SRM, so I take it as given. I burn around 800-900 calories an hour (high intensity race training predominantly).