How to Calculate a Pension Lump Sum: Inputs, Rates, and Timing

To calculate a pension lump sum, you take every monthly payment you’re projected to receive over your lifetime, weight each one by the probability you’ll be alive to collect it, and discount all of them back to today’s dollars using the interest rates and mortality table the IRS requires your plan to use. The three inputs that drive the result are your accrued monthly benefit, the IRS minimum present value segment rates for the applicable month, and the static mortality table published for the plan year. For January 2026, those segment rates are 4.03%, 5.20%, and 6.12%.¹

The Three Inputs You Need Before You Can Calculate Anything

Your Accrued Monthly Benefit

This is the monthly amount you’ve already earned, payable starting at your plan’s normal retirement age. It appears on your most recent annual pension statement or Summary Plan Description, and your plan administrator can provide it on request. Every other step in the calculation is just converting this stream of future monthly payments into a single present-day dollar figure.

The IRS Mortality Table

Federal law requires plans to use a specific unisex mortality table when calculating lump sums, so every plan works from the same life-expectancy assumptions rather than making its own.² For distributions during stability periods beginning in 2026, the IRS published updated static mortality tables and directs plans to use the “Unisex” column for minimum present value calculations.³ The table gives you the probability of surviving to each future age, which becomes the probability that each future monthly payment will actually be paid.

The Minimum Present Value Segment Rates

The IRS publishes three interest rates each month specifically for lump sum calculations under Section 417(e)(3). These are not the same as the funding segment rates actuaries use to measure a plan’s overall obligations; the minimum present value rates apply to individual distributions.⁴ Each segment covers a different time horizon:

The first segment rate applies to payments expected within the first five years.
The second segment rate applies to payments expected between five and twenty years out.
The third segment rate applies to payments expected beyond twenty years.

For January 2026, the three rates were 4.03%, 5.20%, and 6.12%.¹ They change monthly, and the month that actually applies to your distribution depends on your plan’s lookback rules, covered further down.

How the Discounting Actually Works

The math rests on one idea: a dollar you’ll receive twenty years from now is worth less than a dollar today, because today’s dollar could be invested and grow. The calculation reverses that growth to figure out what each future payment is worth right now.

For each month of projected payments, you multiply the monthly benefit by the probability you’ll be alive to receive it (from the mortality table), then divide by a discount factor built from the applicable segment rate. Payments in years one through five use the first segment rate. Payments in years six through twenty use the second. Everything beyond year twenty uses the third, and because that segment covers the longest horizon, it does the heaviest discounting.

Each month’s calculation produces a small present value. Add them all together and you get the total lump sum. As a simplified illustration: if your monthly benefit is $2,000 at age 65 and the mortality table projects payments through age 88, the calculation discounts roughly 276 monthly payments (23 years), weighted by survival probability and sorted into three interest-rate buckets based on when each falls.

Payments far in the future get hit twice. They’re less likely to be paid (lower survival probability) and more heavily discounted (higher segment rate). That’s why the last decade of projected payments contributes relatively little to the total, even though the monthly amount is the same.

Why the Month You Take the Distribution Can Change the Number

Segment rates and lump sums move in opposite directions. When rates go up, lump sums go down; when rates drop, lump sums rise. A one-percentage-point swing across all three segments can shift a lump sum by 10% to 15% or more, depending on your age and benefit size. Someone with a $3,000 monthly benefit could see a difference of $50,000 or more from rate movement over a few months.

You don’t necessarily get the rates in effect the month you request the distribution. Most plans designate a “lookback month” and a “stability period” that together determine which month’s published rates apply to distributions in a given window. A stability period can run anywhere from one month to a full year, and the lookback can reach one to five months before the stability period starts. Your plan document specifies the combination your employer chose. Ask your plan administrator which month’s rates apply to distributions in the current quarter before you commit to a distribution date.

Plan Features That Change the Result

Cost-of-Living Adjustments

If your pension includes automatic cost-of-living adjustments, the calculation has to account for future payments being larger than today’s benefit. Each projected monthly payment gets an assumed annual increase, which raises the total stream of future cash flows and therefore the present value. Plans without a COLA calculate on a flat monthly benefit for life.

Early Retirement Subsidies

Many plans reduce the monthly payment by less than what’s actuarially equivalent when you retire before normal retirement age. Whether that subsidy gets built into your lump sum depends on the plan’s specific language. Some plans calculate the lump sum based only on the deferred benefit payable at normal retirement age, stripping out the early retirement subsidy entirely. If your plan offers generous early retirement terms, the subsidized monthly annuity may be worth more than the lump sum figure suggests.

The Annuity Form You Would Have Received

The lump sum itself is calculated from the present value of your accrued benefit, not from which annuity form you would otherwise have chosen. But the comparison matters when deciding whether to take the lump sum at all. Your plan administrator must give you a relative value comparison that expresses the lump sum and each available annuity form in comparable terms, so you can evaluate the tradeoff without doing the actuarial math yourself.⁵

Getting a Formal Number From Your Plan

Most employers offer an online benefits portal that will generate a lump sum estimate for a projected retirement date. For a binding figure, submit a written request to the plan administrator or Human Resources, and specify the exact distribution date you want the calculation as of, so the administrator uses the correct segment rates.⁶

The plan can take up to 90 days to respond, or 180 days if it notifies you that an extension is needed.⁶ The response comes as a distribution package showing the exact lump sum amount, each available annuity option, the relative value comparison, and a deadline for your election.

Verify the Inputs Before You Sign

Don’t assume the plan’s calculation is correct. Confirm the monthly benefit amount matches your most recent statement, ask which month’s segment rates the plan used, and check that the mortality table matches the current year’s published table. If a number looks off, request the specific inputs the administrator used; you’re entitled to that information. If you dispute the amount, you have at least 180 days from the determination to file a formal appeal.⁷

Two Limits Worth Knowing Before You Commit

If you’re married and your pension is covered by ERISA, you can’t elect a lump sum on your own. Federal law defaults married participants into a qualified joint-and-survivor annuity, and choosing a lump sum instead requires your spouse’s written consent, signed within 180 days of the distribution date and witnessed by a notary public or plan representative.⁶ A general waiver isn’t enough; the consent must name the lump sum form specifically. If your spouse refuses, the plan pays the default joint-and-survivor annuity.

The other limit involves plan failure. If your single-employer plan terminates and the Pension Benefit Guaranty Corporation takes it over, lump sum payouts are heavily restricted: you can only elect one if your total benefit value is $7,000 or less for plans terminating in 2024 or later.⁸ Above that threshold the PBGC pays a monthly annuity for life, subject to its own guarantee limit; for 2026, the maximum monthly guarantee for a 75-year-old retiree on a straight-life annuity is $23,680.90.⁹ If you’re weighing a lump sum offer from a plan you suspect is in financial trouble, that cap is part of the calculation.

1
Internal Revenue Service. Update for Weighted Average Interest Rates, Yield Curves, and Segment Rates
2
Office of the Law Revision Counsel. 26 USC 417 Definitions and Special Rules for Purposes of Minimum Survivor Annuity Requirements
3
Internal Revenue Service. Updated Static Mortality Tables for Defined Benefit Pension Plans
4
Internal Revenue Service. Minimum Present Value Segment Rates
5
eCFR. 26 CFR 1.417(a)(3)-1 Required Explanation of Qualified Joint and Survivor Annuity and Qualified Preretirement Survivor Annuity
6
U.S. Department of Labor. FAQs about Retirement Plans and ERISA
7
U.S. Department of Labor – Employee Benefits Security Administration. Benefit Claims Procedure Regulation FAQs
8
Pension Benefit Guaranty Corporation. Annuity or Lump Sum
9
Pension Benefit Guaranty Corporation. Maximum Monthly Guarantee Tables