The employee's Social Security tax rate for 2018 (January 1 through December 31, 2018) is 6.2% of the first $128,400 of wages, salaries, etc. An employee's 2018 earnings in excess of $128,400 are not subject to the Social Security tax.
[In 2017 the employee's Social Security tax rate was 6.2% of the first $127,200 of wages, salaries, etc. An employee's 2017 earnings in excess of $127,200 were not subject to the Social Security tax.]
The Social Security tax is one of the two components of the FICA payroll tax. The other component is the Medicare tax, which applies to every dollar of an employee's earnings. (In other words, there is no wage limit or cap for the Medicare tax.)
In addition to the employee's Social Security tax, there is also an employer's Social Security tax.
