Calories calculation formula needed for a very cool free bikers app ;)

Your best bet is the online formulas you've already seen. Yes they're very generic and are loose estimates because they don't take into account actual:

- Riding terrain (uphills, downhills, flat...)
- Wind conditions (tailwind, headwind, calm)
- Rider's position as it impacts aerodynamics (makes a big difference on flatter terrain and during descents at speed)
- Rolling resistance of tires (racing tires, mountain bike tires, commute tires, rough roads, smooth roads, dirt, gravel, it's all different)
- Ride dynamics and energy spent on accelerations and lost to braking (traffic stops, technical riding, excessive braking,etc.)

For riders with power meters on their bikes it's pretty easy. Dietary Calories ~ 3.6*average_power*ride_hours
with a small estimation error for the difference between different rider's Gross Metabolic Efficiency (GME)

The trouble is that riders of the same weight, age, etc. on different bikes on different terrain in different wind conditions require vastly different average power to maintain the same speed. So speed only formulas that don't take into account a lot more information than you've listed are going to be very rough estimates at best.

-Dave

30 calories per mile is about as good as any other. Just as bad also.

I have a power meter. It shows about 1500 Joules for about 50 miles. Not enough day to day difference to make me change my diet or my distance.

I guess any formula you can find is good enough.

nikpink, those variables simply aren't enough to accurately estimate calorie consumption.

I read somewhere a very rough guideline that makes a lot of sense. I usually use it when my garmin tells me that I only burned 300 calories time trialling a mountain because my avg speed was only 10 mph. This is really rough but it can be used for context when the formula gives a number that sounds off.

5 calories a minute is about the minimum, 10 calories a minute is pretty hard work for an untrained cyclist or steady aerobic work for a trained cyclist, 20 calories a minute is a very hard effort for a trained cyclist (like a TT or hill climb. It is really not sustainable for an untrained cyclist), and much above 20 calories per minute is probably not sustainable by anyone using a formula to estimate calories burned during a ride.

Quoted post said:

Originally Posted by quenya [IMG]/img/forum/go_quote.gif[/IMG] 5 calories a minute is about the minimum

Which makes sense for reasonably sized adult males as it translates to roughly 88 watts average power but it'd be a bit high for untrained smaller cyclists. I work with a couple of women cat 4's for whom 88 watts is solid Tempo but then they don't weigh very much.

Quoted post said:

,
10 calories a minute is pretty hard work for an untrained cyclist or steady aerobic work for a trained cyclist,

10 Calories per minute ~ 165 watts AP

Quoted post said:

20 calories a minute is a very hard effort for a trained cyclist (like a TT or hill climb. It is really not sustainable for an untrained cyclist),

~ 330 watts AP so pretty hard work for most reasonably sized amateur cyclists but not that high for elite cyclists with FTPs upwards of 6 w/kg

Not bad guidelines, but they should be weight scaled to take into account larger and smaller athletes. I'm always amazed at how little even some of the Cat 3 women I've worked with burn per hour relative to what I see in my files but they're going plenty hard and churning out the watts per kilogram just with a lot less kilograms.

-Dave

Don't make the problem harder than the accuracy of the data inputs.

Quoted post said:

Originally Posted by An old Guy [IMG]/img/forum/go_quote.gif[/IMG]

Don't make the problem harder than the accuracy of the data inputs.

And don't oversimplify to the point where the outputs are worthless.

30 Calories per mile may track your data very well, it will not for someone much lighter, heavier, more or less powerful than you. I regularly burn 750 Calories per hour or more on training rides, that's more than double what I see for some of my lighter athletes and even for some of the heavier but less trained folks I work with. I also review training files from larger racers, some in lower categories who're burning closer to 1000 Calories per hour during focused training. There's roughly a 3:1 spread in the hourly burn rate I see based on power files from the athletes I work with.

It gets back to the original advice given above, you're better off just using the accepted online sports calorie estimators as they've already been down this road and have acknowledged a lot of the uncertainty but have at least provided reasonable estimates based on gender, weight and speed which is far better than 30 Calories per hour as any kind of universal estimate.