When calculating your Series of Substantially Equal Periodic Payments (SOSEPP), provided for under §72(t)(2)(A)(iv) of the Internal Revenue Code, one of your choices is the Fixed Annuitization method.
Calculating your annual payment under this method requires you to have the balance of your IRA or 401(k) account and an annuity factor, which is found in Appendix B of Rev. Ruling 2002-62 using the age you have reached (or will reach) for that calendar year. You will then specify a rate of interest of your choice that is not more than 120% of the federal mid-term rate published by regularly the IRS in an Internal Revenue Bulletin (IRB).
Once you’ve calculated your annual payment under the Fixed Annuitization method, your future payments will be exactly the same until the SOSEPP is no longer in effect. There is a one-time opportunity to change to the Required Minimum Distribution method.
For more details on the Series of Substantially Equal Periodic Payments (SOSEPP) see Early Withdrawal of an IRA or 401(k) – SOSEPP.