How many calories does it take to...

I was asking myself the same question today, (running would be so much easier, shame about the continual overuse injuries.. )

If anyone's got any better answers (other than a Power Meter) than this rule of thumb please let me know..
http://www.drmirkin.com/fitness/8841.html
10mph 26cals/mile
15mph 31cals/mile
20mph 38cals/mile
etc

I assume cyclecomputers that estimate calories use some conversion table like that, you could always scale up/down for weight i suppose..
but then again it would be invalidated by hills ( more air resistance downhill so av speed lower for same cals etc), headwinds .. I wondered if HRM's based estimates would be any better .... get estimates based on time in/below/above zones, calibrate yourself a table on a gym-bike.. ? .. but elsewhere on these forums I've seen people post 'there is no relationship between HR & cals beyond higher=more'.

Personally, to date I have found going on 'time in HR zone' rather than distance/speed more usefull for getting lean,
i.e.
[1] Staying motivated that you're getting benefit when crawling along battling heavy headwinds; and
[2] Primarily using HILL-CLIMBING where the resistance is more linear like running I think, more benefit without losing time at the wrong cadence / gear.

... however that doesnt' answer your question at all: I never maintain weight I am always gaining or losing !

I'm trying to get more scientific and am now graphing weight / BF (tanita scale) / cals / miles. I hope to be able to look back and get an answer via Excell, but this will take some time..

Even then I do a fair amount of weight training and I've no idea how to est cals for that. Enough. My head hurts.

Yes I'd be very curious to hear any replies to this question..