The standard mileage rate is 54 cents per mile whether you are self employed or are an employee. If you are an employee and were reimbursed for your mileage expense then you cant claim that.
If you are self employed, please refer to page 6 of the IRS instructions for Schedule C, under the heading, "line 9" for more information. https://www.irs.gov/pub/irs-pdf/i1040sc.pdf.
If you are an employee, please refer to the following Turbo Tax FAQ for more information. https://ttlc.intuit.com/replies/3300622