FERS military buy-back calculator: what the deposit costs and what it adds
Not sure of your pay? DFAS's Military Buy Back Estimator gives an estimate, and form RI 20-97 gets you the official earnings.
Some of that pay was in 1999 or 2000
Spot a number that looks wrong? Tell us. Everything here runs on your device, and nothing you enter leaves it.
The rules behind the math
The deposit covers post-1956 military service, and the service must have ended under honorable conditions. You pay it to your employing agency before you separate. Payments are not refundable, and filing the paperwork does not commit you to paying. DFAS: Military Service Buy Back.
DFAS says no interest is assessed if you apply within three years of civilian service, and there may be interest after that. OPM sets the rate each year, and it is 4.25% for 2026, compounded annually. This page uses 4.25% for every year past the third. Your real rate changes by year and your payroll office figures the amount. OPM: BAL 26-301.
FERS pays 1% of your high-3 for each year of service, or 1.1% if you retire at 62 or later with at least 20 years. Bought-back years count in both, so they can lift you to 20 years and to the 1.1% formula on all of your service. This page does not check when you can retire, and it leaves out survivor reductions, cost-of-living raises, and taxes. OPM: FERS computation.
OPM says you cannot get credit for military service in your FERS annuity while you receive military retired pay, unless it is for a service-connected disability incurred in combat or caused by an instrumentality of war, or under Chapter 1223 of Title 10, a Reserve retirement. Otherwise you can waive the retired pay, by writing DFAS at least 60 days before you retire, and you must still pay the deposit. OPM: Military Retired Pay.
Fill out form RI 20-97 to get your estimated military earnings, with your DD-214. Then work with your agency's HR or payroll office on Standard Form 3108 and the payment, by payroll deduction, installments, or a lump sum. DFAS has the steps. Need your DD-214? Our guide has the path.
Before you decide
Your agency's HR or payroll office and OPM decide what you owe and what counts. This is an estimate from the figures you enter, not a bill and not a benefit determination. It does arithmetic and shows both sides, and it does not say whether to buy back your time. See Full disclosures.
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Sources
Read October 31, 2026. OPM: service credit, military retired pay, FERS computation, Benefits Administration Letter 26-301, Standard Form 3108. DFAS: Military Service Buy Back and the Military Buy Back Estimator.
