Well the sitting on the train one is a good example. Does my 30 mins actual work include a mark up to cover travelling time too or do i apply my normal hourly rate to the whole lot?
Quite.
For me, what it comes down to is how much I expect/want to be paid (including the 'fixed overheads' for being away from my base (not able to do any other paid work) for a 10-hour day, which, similar to robin, includes an expectation that up to 2 hours of that may be spent in travelling (comparable to commuting to/from employment). I then divide that figure by 8 to get a rough notional hourly rate to use in my calculation for quotes/charges.
As I've said, if travel appreciably beyond that expectation is required, I usually charge about half of that notional rate for additional travel time - although, as I've also said, that ceases to be 'reasonable' (for me) when, in exceptional cases such as I mentioned, virtually all of the total time (away from home) is actually travelling time.
A tradesman might work 60 hours a week on average doing 40 hours chargeable work. ... So might charge an extra 50% per hour on his wage to compensate.
Indeed, as I've said, even my notional 'hourly rate' assumes that 40 hours of 'chargeable work' will' on average' (!) involve at least 50 hours of 'work' (including travelling etc.). However, as I keep saying, that notional hourly rate should, when possible, be 'private' (not exposed to the customer) and merely used by the tradesman to calculate totals for quotes/charges. Hence, it doesn't matter on what basis the hourly rate is determined, provided that the tradesman uses it appropriately in his/her calculations.
I wrote 'if possible' since I, for one, function in a world obsessed with 'hours' and 'hourly rates'. It's really very silly since all it means is that one has to adjust ones 'claimed hours' so as to achieve the total one wants on the basis of whatever a client regards as 'the hourly rate'!
In practice, it's actually much more complicated (and 'worse') than that for me (and people like me), since the great majority of clients seem totally unable to understand the concepts like 'thinking time', 'researching time', 'checking time', 'proof-reading time'' etc. etc. That means that I (and everyone else) am only able to charge (without endless argument) for much less than half the hours we sit at our desks, in front of our computers or whatever, as a result of 'doing the work'. However, that's again very silly, since it has merely resulted in the 'hourly rates' which clients accept as 'the going rate' being what you would probably regard as 'astronomical' - probably at least three times higher than it would be if we could charge (without argument) for the true number of hours 'expended'.
Please forgive my use of the term - average- it is probaly the most dangerous word in the universe
Certainly one of the most abused/mis-used words in the universe but, given that virtually nothing is without variability, also one of the most useful words/concepts in the universe - since the alternative (one-off anecdotes) is even worse
Kind Regards, John