See this list of US freelance editing rates in US dollars.

Here is another method of working out your rates (put in your own numbers). All figures are in Australian dollars.

Annual figures:
Yearly living expenses (rent, bills, food etc.) = $13,000
Round up figure to the next big number and assume that this what you aim to earn for the year = $20,000
Profit before tax = $20,000 – $13,000 = $7,000
Check the tax rate (take a look at the ATO website) = $4,000
Profit = $3,000

Not good enough! A profit of $3,000 gets spent really quickly.

Double the first annual income figure = $20,000 x 2 = $40,000
After expenses = $40,000 – $13,000 = $27,000
Tax rate = $6,000
Profit after tax = $27,000 – $6,000 = $21,000
Reinvest money into business (equipment, training, marketing) = $10,000
After reinvesting, final profit = $11,000

To calculate your hourly rate:
Weeks in the year = 52
Holidays = 4 weeks
Left with = 52 – 4 = 48 weeks
Sick days (for sleeping in/sneezing/feeling miserable) = 2 weeks
Left with = 46 weeks
Divide $40,000 by 46 = $800 odd is what you need to make per week.
How many hours will you work per week? = 20 (20 is part time, 35-40 is full time)
Divide $800 odd by 20 = something around $40 ish.

Base hourly rate = $40 (this is as low as you should go such as when you give a discounted rate)
IPEd recommended rate = $65 per hour.
MEAA rate for 2009 for freelance book editors & proofreaders = $846 per day, $564 per 1/2 day & $211 per hour.

You can take a look at the MEAA rate guide here and the IPEd recommendation on rates here.