According to FICA, you must contribute 12.4 percent of your earned income up to the predetermined limit of contributions, and another 2.9 percent must be contributed to Medicare. It is important to note that there is no earnings limit on the Medicare portion of the tax, and thus in practice one is taxed 2.9 percent of all earned income, regardless of your total income level.
For those working for hourly wages the tax levels are different. Hourly employees contribute 6.2 percent for Social Security and 1.45 percent for Medicare. Hopefully you noticed that this is just half of the standard rates. There is good reason for this as your employer is required to pay the other half of the rate for Social Security and Medicare contributions. In other words, for those working at hourly wages, the employer must match the employee contributions.