According to Obamacarefacts.com, the average American will pay 3% - 9,5% of their MAGI (modified adjusted gross income) on health insurance premiums. How to calculate MAGI can be found a IRS.gov. Also, premiums can vary from state to state and can vary depending on age, weight and smoking status, but not on health status or gender.
If you are making an average middle class income or higher ($60,000), expect to pay premiums closer to the higher end. For a family of 4 making $60,000 will likely pay premiums of around 9% or $5,400 per year ($450 per month). If you are single making just $32,000 a year, you will pay premiums of around 9% or $3,000 per year ($250 per month). For most, these premiums are a significant increase. However, some will pay nothing or minimal premiums if they are close to or below poverty level income. For a family of 4 making $32,000 or less, you would be Medicaid eligible in most states. For a single person, income would be closer to $16,000 in most states. These calculations are estimates only and can change depending on your state, weight, smoking status, and MAGI.
In an article today at Forbes, it was found that Obamacare will increase premiums for a 40 year old on average 99% for men and 62% for women. For a 27 year old, Obamacare will increase premiums on average 97% for men and 55% for women. That means, if you are a 27 year old male and your current premium is $200, you new premium will be $394. Yikes! If you are a woman, the increase isn't as shocking but who wants a 55% - 62% increase in premiums. Keep in mind that these are averages and states vary from slight decreases to increase of over 300% depending on age. The article has an interactive map that you can use to click on your state to get an estimate of what you might pay in 2014.