kilojoule to calorie

gee.bike

what is the coversion when from a kilojoule to a caloire when related to cycling.

ric_stern/RST

i assume you mean from a kilojoule to the usual measure of food energy of kcal (kilocalorie). That is you divide by 4.18 (or multiply in the other direction).

However, as you are asking about cycling and this is the power training section i assume you are measuring kj on a power meter (e.g., PT, SRM, etc) and want to convert to kcal as maybe a measure for dietary intake??

You would still divide by 4.18 to convert to kcal, e.g., you do a ride and your meter says you expend 2000 kj. This is ~ 480 kcal. However, cyclists are ~ 20 - 25% efficient (you would need to measure this in a lab, but the figure will vary with cadence, absolute power, environment and topography, etc), so you multiply that ~ 480 kcal out by 4 to 5, to get your ball-park measure on energy expenditure, i.e., 1920 to 2400 kcal.

As you won't know *exactly* how efficient you are at anyone time, you're likely best off just taking the reading in kj from a power meter and changing it to kcal. In this case saying, i expended 2000 kj on my meter, that's about 2000 kcal.

ric

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