Could you expand on this at all? Why so few billable hours? I can understand why it's not 10/10 (administrating your own work, keeping records, billing clients) but just 40% of your time? What kind of things are taking up the other 4 - 6 hours that can't be billed?
that will probably take 60-120 minutes of your day.
driving to clients for meetings. may be billable, may not be.
driving to potential clients for meetings, and having those meetings - not billable.
dealing with incoming calls and emails.
actually trying to market yourself - blogging, or some other content work, or applying for conference speaking, or planning presentations for local groups (tech groups, business meetups, etc).
debugging crap that doesn't work.
dealing with taxes/payroll/accounting/recordkeeping/insurance.
needing time away to deal with life emergencies or other events.
6 billable - as in, solid productive - *consistently - as in, weeks or months at a time - is generally very hard to pull off for most people. You can certainly be 'on the clock' for more, but just as in about any mental job, you'll have ebbs and flows, and some of that time won't be terribly productive.
I would also include in my billing a 30 minute lunch over an 8 hour day, which is the minimum mandated by local (Canadian) labour law, and I would bill for any incoming calls and email that is related to the project I'm working on.
I'm definitely aware of how different my time feels when I'm billing, and I've tried to relax a bit. I think billing daily or weekly is always better than hourly.
That said I understand getting to daily or weekly rates can really let your rates take off, and you don't have to worry about what time you're on the clock in the same way.
I get being hesitant to bill for certain kinds of troubleshooting, but I think it comes down a lot to what the scope of the project is. If I'm on something that is multiple weeks of work, and I'm dealing with a problem that I would be encountering and would be expected to solve if I were working full-time, then it's billable.
If you bill daily or weekly, then great. If you bill hourly, then the only way this is okay is if you put "30 minutes lunch" on your bill and show that you're charging for it. There's a reason why it's very very hard to bill for 8 hours of work in a day, and that's because you don't work for 8 hours.
If your client understands and expects to be billed for lunch, and your client is paying for your time from 9-5, then it's reasonable. (But that would be a rare situation, normally that would be very temporary, or become a full-time salaried position). If your client is paying for your work on an hourly basis, and has not explicitly agreed to pay for your lunch, then billing for it should be off limits.
For most hourly contract work, lunch is on your own time, not billable hours. I'd be pissed if my lawyer were billing me for lunch, it would be downright dishonest.
As far as debugging, I assumed the parent's comment was talking about debugging his own tools, for example a debugging activity that applies to all his clients, or to himself, rather than time spent on project specific triage. If I'm working directly on the project, I bill for it. If I'm working on something that is indirect and/or not solely for the project's benefit, then I don't.
The overhead of recording time and dealing with every call and email ends up being - for me - way too much time/recordkeeping. Scheduled calls/meetings, yes. Someone has a 3 minute call where I can answer a followup question - I just answer it. "But you'll be interrupted all the time with 3 minute calls!" - except, if I'm too busy or don't want to be distracted... I just don't take the call.
Daily/weekly can be, if the clients are OK with that too. I've found some that aren't. along with that, I typically have multiple projects running simultaneously, and I can't - in my mind - ethically charge for a 'day' if I've split my time on 2-3 projects that day.
I don't like charging for time at all, really, but some orgs aren't really set up to handle any other mode of work (and/or, want flexibility in change, so time may be the least unfair approach).
It depends on the job and also on your philosophy and your contracting rate, of course, but I bill only for hours that I’m actually physically in my chair working on the project, and nothing else. Speaking with other contractors, this seems like the norm to me.
Even if you’re not working, a very enlightening and worthwhile exercise is to track your time to the minute at your day job and find out how much you’re actually working. I use toggl to track my time (which I’m not endorsing, use anything that’s tolerable and convenient enough, it’s not like time tracking is fun). Toggl stops tracking after a configurable x number of minutes idle, I use 5. I stop tracking while I’m emailing or reading hacker news. I also don’t track time spent billing; putting together reports on my time & progress and such.
If you’re like me or most people, you might be really surprised to find out that breaks and office chatter and surfing and lunch actually consumes 20%-40% of your work day.
Plus who can work a 10 hour day consistently?