Try for 5.5-6.5.
Try for 5.5-6.5.
From previous experience, 80% productive time is considered high-acceptable and 60% is getting to the low end. Depends on your role as well.
Also as a general rule, cost multipliers are important. Standard multiplier of 2.3x of costs (then margin on top) seems to work out about right - longer term / safe / secure projects can go a little lower if you know we can bill consistently, a higher multiplier if the work is less certain / short term.
I am having somewhat of hard time working with clients who do not want fulltime though because:
a. Even though they pay only 20 hours of my time, they assume 100% availability. b. It gets awkward with them when they suddenly want to increase the hours but I have already committed my remaining hours elsewhere.
You need what's called a retainer agreement. It will specify an exact amount of time they have to pay you for every X, as well as specify availability and charge for it. It will literally specify what availability you have to give them, and how much they are paying, specifically for that availability, and that you are working for other clients and will not necessarily be able to change the terms of the agreement without several weeks/months notice.
(Additionally, retainers are often paid in advance, not arrears :oD, and charged wether they have work for you to do or not)
If you can find a client who only wants you for 2 hours a week, would you take it? I wouldn't.
I'm curious on how to do a fair calculation on this because, to be honest, I do spend a lot of time (that can't be calculated) thinking about the problem at hand, etc.
Anybody who is thinking about how many hours you spent "thinking", "noodling", "coding", "typing", "documenting", "eating lunch", "reading web comics", or "posting on HN" is a client you need to avoid.
If you're constantly pulling 60 hour weeks (about what you have to pull to bill 40 honestly), you're likely delivering what I am pulling 35-45 hour weeks, billing 25-35, but at a higher cost to your family/health/rest of your life.
That's not adult. That's slavishly burning yourself out in your early years.
Study: http://www.hcgexperts.com/scheduled-overtime-effect-on-const...