I've found a good (albeit a bit conservative) rule-of-thumb is to convert the hourly wage into the yearly salary. Working as a consultant for $175/hour is similar to being employed at $175K/year.
EDIT: The U.S. federal self-employment tax for 2011 is 13.3% (15.3% was for 2010).
However, for 2011 the FICA rate for employees is 4.2% instead of 6.2%, so the self-employment tax remains effectively 7.65%. But that's only for the first $106,800 in earnings - everything above that is not subject to FICA and Medicare for employer and employee.
It is a myth that America is a low tax nation.
http://en.wikipedia.org/wiki/Government_spending#Government_...
In American those taxes provide a strong military. Most of the rest of the world are very poorly equipped by comparison. Other countries get health care and education.
The differences in tax between the US and Australia are not so much in the headline rates as in the deductions.
In the US mortgage interest on a home you live in is tax deductible.
And in the US you get taxed as an economic unit with your spouse and children.
So a home owner with a big mortgage and a spouse at home looking after kids pays much less tax in the US.
Also the overhead of running a corporation (including lawyer, accountant, payroll, and general insurance) is not much if you're making over $100/hr. It is certainly less than 26.7% (ie, $75 of every $175 minus 15.3%) worth. Most of these costs are fixed, not variable.
The general rule is always "times 2, add 3 zeros" to do it in your head.
But yes, this is generally the rule I use as well, take the hourly rate and double it and add a K (eg $30/hr = $60K)
Doesn't include holidays, sick leave or efficiency trade-offs (billable time vs maintenance, research). Personally I use an estimate of about 75% efficiency to get a realistic answer, so then your formula becomes 3/4 * x * 1000
So at $175/hr I'd expect something like 130,000 annually. Given that its said he's quite frugal and doesn't mind hard work, it could well end up being around the 250-300K, but I'd expect he'd end up burning out after a year or 3.
3/4 on it's own is less than %40 efficiency. I.e. Taking half the year off.
You also just stated the same thing slashcom did while meaning to correct him?
But hey, at 75% efficiency at a half year's work at that rate I could probably afford it...
$40/hr => 80k/y $120/hr => 240k/y