In reply to Daniel Heath:
> (In reply to SARS)
>
> Sorry I don't have an answer, but it's an interesting idea.
>
> I doubt you burn that many calories. Forearm muscle are very small, you probably burn similar calories walking up stairs the same height (covering the same distance).
Climbing involves a little bit more than just forearm muscles.
> After some Googling it appears that one pull up burns less than a calorie.
And it's not just a series of pull ups.
Rockovers, mantling, heel hooks etc. all use leg muscles and you'll be using muscles in your trunk to keep yourself on the wall. This is especially true for more overhanging routes, so to say easy climbs use less calories than hard climbs is probably not right.
Bouldering in particular is very gymnastic so perhaps look into how many calories gymnasts burn as a rough guide?