# Calculating Calories Burned



## Taskmaxter

All, just trying to find a rough estimate on what the best way to calculate calories burned. I've been doing some longer rides with a lot of climbing and would like to know an approx burn for a ride. Anyone using a web site or standard rule of thumb that they wouldn't mind passing along?

Thanks!


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## Kerry Irons

*Two options*



Taskmaxter said:


> All, just trying to find a rough estimate on what the best way to calculate calories burned. I've been doing some longer rides with a lot of climbing and would like to know an approx burn for a ride. Anyone using a web site or standard rule of thumb that they wouldn't mind passing along?


Either way, this is a little tedious because you need to break your ride up into segments where you know the slope and your speed. That said, you can get pretty good numbers from analyticcyling.com. The results are in watts, so multiply by 3.6 to get calories. Alternatively, you can use the following formula to calculate calories (same underlying formula as used by analyticcycling.com):

calories/hr = [V*W(.0053 + %G/100) + .0083(V^3)]*7.2
watts = [V*W(.0053 + %G/100) + .0083(V^3)]*2

where V is speed, W is bike + rider weight in lbs., and %G is grade in per cent. The factors listed here (0.0053 for friction + rolling resistance and 0.0083 for aerodynamic drag) are obviously not absolute. They will vary with efficiency of the tires and drive train, and with the aerodynamics of the bike + rider combination. Both of these assume a racing position on a racing bike. A clunker bike or a more efficient riding position will change these numbers, which are averages anyway. Power to overcome friction and gravity is proportional only to rider weight and ground speed. Power to overcome wind drag is proportional to the cube of the air speed. For reference, 1 hp = 2700 calories (because of human metabolic efficiency of 24%); 1 calorie = 0.276 watts; 1 hp = 746 watts. Here, all calories are kg-calories, or "food calories."

If all of this is too complicated, then 30-35 calories per mile is not a bad average estimate for 20 mph on flat ground.


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## prschatt

One word... Powertap


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## Cervelo-er

One cheaper word...HRM...wait, that's three words...what a deal!


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## TurboTurtle

Cervelo-er said:


> One cheaper word...HRM...wait, that's three words...what a deal!


May be cheaper, but it doesn't have a clue as to how many Calories you burned. I think it was Zinn that called them random number generators. - TF


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## Cervelo-er

*If all you need is a rough estimate...*

To quote the OP:

""All, just trying to find a rough estimate on what the best way to calculate calories burned. I've been doing some longer rides with a lot of climbing and would like to know an approx burn for a ride.""

HRM does that for about $50 or less for the basic ones.

MapMyRide.com also does a workout estimator if you want a "rough estimate".

Of course a PowerTap would be better...but you'd still be taking just a more accurate look at a moderately estimated number.

Does the PowerTap calculate your BMR? Does it account for everything else going on in your body for the 2-6 hrs you're out riding? Does it account for absorbtion rate differences for your unique GI tract?

My point is, everything is going to be a best estimate to some extent, so unless you want all the functionality of the PowerTap for other reasons, there are easier/cheaper ways to get a rough estimate.



TurboTurtle said:


> May be cheaper, but it doesn't have a clue as to how many Calories you burned. I think it was Zinn that called them random number generators. - TF


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## iliveonnitro

HRM calorie counters are usually 30-80% high. Or, as Zinn said and TurboTurtle quoted, "random number generators."


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## iliveonnitro

Also, the powertap measures, quite accurately using strain gauges, the number of kJ you produced in a ride. Since, after factoring body efficiency, it is within ~2-3% of your actual Calories burned, it is a great tool for knowing Calories burned.

You can test your BMR and factor in other caloric concerns off the bike. But for on-the-bike training, it is an accurate number. 

Eg) My BMR is 1800Cal/day. Mildly active puts me around 2400Cal/day. Read the kJ on the powertap after my ride (say, 2000Cal), and I should consume 4400Cal to break even. The MOST inaccuracy in this knowing my "mild active" state and how many Calories I burn while walking to class, work, eating, etc.


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## Cervelo-er

*Point taken...*

I think I'm just grumpy from not being able to justify the $1K for a PowerTap myself yet...



iliveonnitro said:


> Also, the powertap measures, quite accurately using strain gauges, the number of kJ you produced in a ride. Since, after factoring body efficiency, it is within ~2-3% of your actual Calories burned, it is a great tool for knowing Calories burned.
> 
> You can test your BMR and factor in other caloric concerns off the bike. But for on-the-bike training, it is an accurate number.
> 
> Eg) My BMR is 1800Cal/day. Mildly active puts me around 2400Cal/day. Read the kJ on the powertap after my ride (say, 2000Cal), and I should consume 4400Cal to break even. The MOST inaccuracy in this knowing my "mild active" state and how many Calories I burn while walking to class, work, eating, etc.


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## Dwayne Barry

Cervelo-er said:


> I think I'm just grumpy from not being able to justify the $1K for a PowerTap myself yet...


The problem with using HR, which is a reasonably good relative measure of how you're working, to estimate calories burned is that you need some absolute numbers to provide useful information. IOW, are you a world class athlete capable of burning upwards of ~1500 kcal/hour or not very fit at all and not able to work harder than 500 kcal/hour?

I think if you can get some handle on that it can be reasonably useful even though it is affected by numerous other factors that have nothing to to do with how hard you're working and hence how many calories you're burning.


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## TurboTurtle

iliveonnitro said:


> Also, the powertap measures, quite accurately using strain gauges, the number of kJ you produced in a ride. Since, after factoring body efficiency, it is within ~2-3% of your actual Calories burned, it is a great tool for knowing Calories burned.
> 
> You can test your BMR and factor in other caloric concerns off the bike. But for on-the-bike training, it is an accurate number.
> 
> Eg) My BMR is 1800Cal/day. Mildly active puts me around 2400Cal/day. Read the kJ on the powertap after my ride (say, 2000Cal), and I should consume 4400Cal to break even. The MOST inaccuracy in this knowing my "mild active" state and how many Calories I burn while walking to class, work, eating, etc.


I've seen estimates of 19-26% for cycling efficiency. The 1 to 1 assumes just under 25%. So you still could be off by over 20%. Still far better than HRM. - TF


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## Taskmaxter

*Thanks*

Thanks everyone - one further question, what is PowerTap? I'm assuming its a device you wear? Someone point me to more info on this tool? Many thanks to you all.


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## Jrmccain

Check out this article:

http://www.analyticcycling.com/CycleOps/PowerTapFeatures.html


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## roadboy

i have used the calorie function on a few of my HRM and the numbers are always way off, usually they all seem really high, like burning 1500 calories per hour. Thats a no way situation, so I would say dont rely on HRM for a calorie reading because they are usually bunk.


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## TurboTurtle

Taskmaxter said:


> Thanks everyone - one further question, what is PowerTap? I'm assuming its a device you wear? Someone point me to more info on this tool? Many thanks to you all.


A PowerTap is way too expensive as a Calorie counter (probably to expensive as a normal training tool). We were just trying to show in inaccuracy of HRM functions other than HR. - TF


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## GTScott

While doing intervals on the trainer with a moderate resistance yielding an average speed of 22-23 mph with intervals at 100-105 rpms, my garmin 305 gives me a rate of about 65 calories per mile or 1425 cal/hour. I throw the Garmin numbers into my spreadsheet and multiply them by 0.58 to get a more realistic guess. I came up with the 0.58 by looking at other data available online and making an educated guess. With this number, I am showing a burn of about 37-38 cal/mile or 825 cal/hour which seems more inline.


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## Dwayne Barry

GTScott said:


> While doing intervals on the trainer with a moderate resistance yielding an average speed of 22-23 mph with intervals at 100-105 rpms, my garmin 305 gives me a rate of about 65 calories per mile or 1425 cal/hour. I throw the Garmin numbers into my spreadsheet and multiply them by 0.58 to get a more realistic guess. I came up with the 0.58 by looking at other data available online and making an educated guess. With this number, I am showing a burn of about 37-38 cal/mile or 825 cal/hour which seems more inline.


I wonder if it is an intentional marketing ploy by manufacturers of gym equipment and these other devices to provide artificially high calorie numbers to entice people to use these products since they think they are getting more "bang for their buck" in a sense?

According to these things it appears that there are unknowing world-class endurance athletes all over the place


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## GTScott

Well, Garmin knows my worldclass ability but I like to factor it down to be on par with the common man. 

I don't know if it is a ploy as much as laziness. With the Garmin recording slope, weight, heart rates, etc. etc it seems that it could do a better job predicting this information.

On another note, compared to tabulated values, it does seem to be pretty accurate with my calories burned while running. Actually, I think it predicts a tad bit low there. Go figure.


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## Kris Flatlander

iliveonnitro said:


> Eg) My BMR is 1800Cal/day. Mildly active puts me around 2400Cal/day. Read the kJ on the powertap after my ride (say, 2000Cal), and I should consume 4400Cal to break even.


How do you come up with your BMR here? I've used the calculator over at FitDay.com and it has me at 1957 basal, with another 1272 through the day (walking all around campus etc throughout the day). Having it at 3230 before I even step on the bike seemed a bit off. I'm currently 19 and 169 lbs at 6'4 if that helps.


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## GTScott

The best thing I have found for calculating your BMR is this spreadsheet. 

BMR Spreadsheet

I had been using this, calculating the base, and then adding in what I burned throughout my workouts to see what I was burning. Recently I was told that this was not correct and that if you want to do a similar setup where you add in your knowns, you should take the calculated BMR and multiply it by the sedentary (1.2) multiplier and THEN add in what you burn. 

For example, my BMR is 1555. I multiply that by 1.2 to get 1866. I then add in my 4.6 mile run at 498 calories, my 45 minute intervals at a modified 600 calories (Garmin's 1035 x 0.58), 140 for a 45 minute 2.5 mile dog walk, and a random guess of 80 for a 30 minute weight lifting routine to get to a total burn of about 3185.


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