stonecrd

Best estimates are based on power and the best on-line power calculator I've used is https://www.kreuzotter.de/english/espeed.htm. If I throw in data for a ride with no climbing, no wind, 20mph for an hour it says 185 watts = 636 kcal. Now add a 2mph wind and you get 214 watts = 736 kcal. You can play around with this to get a pretty good estimate, better than I get with my HRM.

This calculator takes into account bike weight, position, rider weight, wind, slope etc and assumes 25% efficiency.

yanos

^Cool website. Thanks for posting it.

SSP

The rule of thumb for cycling is 40 calories per mile.

Snuffleupagus

Who says way less?

The only thing I've seen indicates way more, as the 1:1 formula assumes a highly efficient cyclist. The guys on the wattage list seem to think that 25% is high for many cyclists, and that many are as low as 20% efficient.

UmneyDurak

I heard that from someone a while back. To be fair I don't think they had a clue what they were talking about.

CdCf

I think you misunderstood. If the kJ reported by the power meter is the average power at the crank, times the total time, then it's only the mechanical power, and the conversion factor to total energy used by the body - assuming a 20 % efficiency - is ~1:1.

Snuffleupagus

That depends upon whether you're assuming 5:1 or 4:1 which is where the 25% number is derived.

TurboTurtle

5:1 or 4:1 what?

The conversion is 1 Kj ~ 0.239 Cal. If you use a 1 Cal for each Kj on the power meter, you are assuming a 23.9% efficiency. I have seen numbers stated in the range of 19-26% for the body's efficiency; usually correlating to 'fitness' (i.e. the more fit, the higher the efficiency). Note that you must first have an accurate power meter before any of this applies.

TF

Roody

What's the point of getting a more accurate estimate of calories burned? Do people actually spend a lot of time calculating the number of calories in and out? How ridiculous. The time spent calculating would be better spent riding your bike. The only measurement that makes a real difference is your body weight on the scales.

umd

If somebody is trying to lose weight, it makes sense to get an accurate estimate. Especially if they normally have trouble "staying on track". It gives a relatively straigtforward method to ensure that you maintain a caloric deficit.

"The time spent calculating would be better spent riding your bike" is not necessarily true. It is really easy to overeat past the excess calories burned, and exercising even more can just make the post-exercise appetite that much stronger. I rode 20K miles last year, with many weeks were over 400 miles and gained weight.

Roody

Except there is no reliable way to measure caloric expenditure on a daily basis. In fact, there's not even an accurate way to measure caloric intake. All the tables you see have different values, and who actually weighs every gram of food that they eat?

Even the best methods of measurement of either "calories in" or "calories out" would probably have at least 5 % error, and that's within the range of the differences that you're trying to measure.

Weigh yourself every week. If the number goes up, eat less and/or exercise more next week. The scales don't lie, and they're fairly accurate.

I do use the 40 calories/mile as a rough estimate, but that's more to motivate myself than to make realistic plans.

CdCf

I do. At least for most of the year. Although I round everything to the nearest 5 g.

And I mainly use the nutritional values found on the packaging. You'll be close enough in the end. Better than 5 % error.