# kJ to Calories help



## bauerb (Jan 18, 2006)

i did 2 efforts:
1. 63 mins, avg power = 277, kJ = 1051
2. 72mins, avg power = 278, kJ = 1205

if I add up the kJ = 2256

an online calculator converted that to 539 calories. Now I was racing during those 2 efforts. I mean basically killing it for 2 hours of crit racing. is that really only 500 cals? like the equivalent of a bagel with a little cream cheese? seriously?


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## den bakker (Nov 13, 2004)

bauerb said:


> i did 2 efforts:
> 1. 63 mins, avg power = 277, kJ = 1051
> 2. 72mins, avg power = 278, kJ = 1205
> 
> ...


500 calories is 25% of "an average persons" daily intake after all. 
more than 40% of the energy in that bagel and cream cheese is from fat by the way....


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## function (Jun 20, 2008)

On a bicycle, assuming 25% metabolic efficiency, kJ ~= Calories so it was more like 2200 Calories.


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## Guest (May 11, 2009)

function said:


> On a bicycle, assuming 25% metabolic efficiency, kJ ~= Calories so it was more like 2200 Calories.


Actually it's a 1 to 1.1 ratio. So 2200 would give you 2400 calories.


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## Wookiebiker (Sep 5, 2005)

The Powertap manual gives you a calculation for converting KJ to Calories...

Basically take your KJ burned x .233 then divide by .22...so in your case 2256 x .233 = 525.648 then divided by .22 = *2389.309 *calories burned.


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## function (Jun 20, 2008)

I'll stick with my point that its easier to just say kJ = Calories, much easier than doing all the calculations in your head.


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## Alex_Simmons/RST (Jan 12, 2008)

function said:


> I'll stick with my point that its easier to just say kJ = Calories, much easier than doing all the calculations in your head.


Indeed and since each rider would have a different metabolic efficiency level, then unless you know your own efficiency (which can be determined via lab testing) then using a specific conversion factor is not all that useful.


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## bauerb (Jan 18, 2006)

thanks guys. I think that 1-1 is close enough for me


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