For 2017 the Social Security taxable wage base is $127,200. You will pay 6.2% social security tax on wages up to that amount. This base increased $8,700 from last year.
There is no limit on the amount of wages you will pay Medicare tax on. That tax rate is 1.45%
If you are receiving social security, the amount of earned income you can have without losing benefits depends on your age.
Social Security will deduct $1 from benefits for each $2 earned over the threshold.
For 2017 the limit is $16,920 for those under full retirment age all year.
In the year you reach full retirement age the limit is $44,880 but they only count the earnings before the month you reach your full retirement age.