Pension COLA Sensitivity Calculator
A pension that pays $4,000/month today won't buy $4,000/month of goods in year 20. Model how FERS, CSRS, and private sector COLA formulas affect your real purchasing power over time at any inflation assumption.
How this calculator works and the math behind itWhy COLA formula matters more than pension size
Two retirees start with the same $5,000/month pension. One has CSRS with full CPI protection. The other has a private sector plan with no COLA clause. At 3% inflation, year 20 looks like this: the CSRS retiree is receiving the equivalent of $5,000 in today's dollars. The private sector retiree is receiving the equivalent of $2,773 in today's dollars, even though the nominal dollar amount is the same as when they retired.
The FERS formula occupies the middle ground. At 3% CPI, FERS gets 2% -- losing 1% of purchasing power per year instead of 3%. That compounds: over 20 years, FERS purchasing power at 3% CPI falls to about 82% of the original, vs 55% for a no-COLA pension. Not full protection, but meaningfully better than nothing.
The breakeven question is whether the inflation protection justifies taking a lower pension. FERS employees who choose the FERS MRA+10 option typically give up the FERS Supplement and delay COLA -- a tradeoff that can cost tens of thousands in cumulative real dollars if inflation runs hot.
Private sector employees with no-COLA pensions often don't realize the risk until year 15 or 20. A pension that felt generous in 2005 feels thin in 2025 after 20 years of cumulative inflation. Social Security with COLA, a Roth IRA, or other inflation-linked assets can fill this gap -- but only if you plan for it.
Frequently asked questions
What is the FERS COLA formula?
Three tiers based on CPI-W: at or below 2% CPI, FERS gets the full CPI increase. Between 2% and 3% CPI, FERS gets exactly 2%. Above 3% CPI, FERS gets CPI minus 1 percentage point. So at 5% inflation, FERS gets 4%. FERS COLAs also only begin at age 62 -- early retirees receive no adjustment until they reach that age.
What is the CSRS COLA formula?
Full CPI-W with no cap or reduction. Whatever inflation runs, CSRS retirees receive the same percentage increase. This is the same protection as Social Security and the reason Congress excluded CSRS employees from Social Security when they created it -- they already had a fully indexed pension.
When does FERS COLA begin?
At age 62 for regular retirees. If you retire at 58 under MRA+10, your pension receives zero COLA for four years until you turn 62. The cumulative cost at 3% inflation over four years is about 12.5% of purchasing power lost before adjustments even begin. Disability and VERA retirees are exceptions -- they receive COLA immediately.
Do private sector pension plans have COLA?
Most do not. ERISA does not require private defined benefit plans to include cost-of-living adjustments. Some plans offer ad hoc increases at the discretion of plan trustees, but nothing contractual. Check your Summary Plan Description. If it doesn't mention COLA, the default answer is no.
How does COLA interact with the FERS Supplement?
The FERS Supplement -- the bridge payment that approximates your Social Security benefit from retirement until age 62 -- does not receive COLA. The supplement is recalculated annually for any earnings over $22,320, but the base payment is fixed. Once Social Security begins at 62 or later, you start receiving full CPI adjustments through Social Security.