Rightsizing Pension Premiums Act of 2017 This bill amends the Employee Retirement Income Security Act of 1974 (ERISA) to: (1) modify the formula that the Pension Benefit Guaranty Corporation (PBGC) uses to calculate the funded percentage of single-employer pension plans, and (2) reduce single-employer PBGC premiums for pension plans that are sponsored by certain small employers or have specified PBGC funded percentages. The bill also prohibits the budget effects of provisions that change PBGC premiums from being counted for the purposes of determining budget points of order for legislation in the House or the Senate. (The PBGC is a federal agency that insures the benefits of private sector, defined benefit pension plans. The PBGC is financed by insurance premiums paid by sponsors of the plans, investment income, assets from pension plans taken over by the PBGC, and recoveries from the companies formerly responsible for the plans.)