I'm not sure what everyone else on the forum thinks about this calculator but I use it as a start and then experiment/tweak from there in training.

http://www.tri-talk.com/TriTalkNC/TriTalkNC.htm

Thanks - that little calculator is useful!

You still need to enter in your calorie needs on the run though - how do I estimate that?

I think trying to replace 1:1 is a recipe for disaster. 3,000 calories for a century might be correct, but if you look at a 1:1 replacement based on time that would be anywhere from 500-600 calories/hour using a 5-6 hour ride.

Same with the run. The 100 calories per mile rule of thumb is a good start, but that's 2,600 calories over 3-5 hours...again, guesstimating.

Start out with 200-250/hour if you're female and 250-300/hour if you're male. Work up from there and base it on 12 ounces of liquid (count the liquid calories if there are any) for 100 calories. 300 calories per hour = 36 ounces per hour. Adjust accordingly.

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Brandon Marsh - Website | @BrandonMarshTX | RokaSports | 1stEndurance | ATC Bikeshop |

General rule of thumb is 300-400 cal/hr on the bike and 150-200 on the run. The three things to stay on top of are calories, electrolytes, and hydration. Test your plan in longer training sessions and work out all the kinks. Some prefer solids, others can't stomach them.

There are suggested values on the right hand side based on the time and intensity you select. Play around with it. My values from the calc fall into the range others have said here but again you need to experiment in training to see what's right for you. Important note already mentioned is that you can eat more on the bike vs the run.