The three numbers that decide your lump sum
Every pension lump sum comes down to three inputs: your monthly benefit (what you'd collect each month), how long you'd collect it (tied to your life expectancy), and the discount rate (an interest rate the plan uses to value future money). Change any one and the lump sum moves.
Step 1 — Total the payments you're giving up
Start with the raw sum: your monthly benefit times the number of months you'd expect to receive it. A $1,800 monthly pension collected for 25 years is 300 payments — $540,000 in total checks. But that is not your lump sum, because money you'd receive decades from now isn't worth a full dollar today.
Step 2 — Discount every payment back to today
A dollar you'll get in 20 years is worth less than a dollar today, because today's dollar can be invested and grow. The plan discounts each future payment back to its value now using the discount rate, then adds them all up. That total is the present value — the honest lump sum. The calculator above does exactly this with the numbers you enter.
Why interest rates swing your payout
Here's the part that surprises people: a higher discount rate makes your lump sum smaller, and a lower rate makes it bigger. When rates rise, plans can promise the same pension with less money up front, so the lump sum shrinks. If your offer window spans a rate change it can move your payout by thousands — see how much with the interest rate impact calculator.
Is the lump sum a good deal?
Calculating the number is only half the decision. Once you know the present value, compare it to what the monthly pension is worth to you — the lump sum vs monthly calculator shows the break-even age, and the buyout calculator flags whether an offer sits above or below the true value. An offer well below the present value means you're being asked to sell your pension cheap.
Common questions
Does the calculation include taxes? No — the present value is pre-tax. A lump sum paid to you is taxed as income (usually with 20% withheld) unless you roll it into an IRA. Estimate the hit with the pension lump sum tax calculator.
What discount rate should I use? Plans often use rates in the 4 to 6% range tied to corporate bond yields. Try a few to see how sensitive your number is.
Why is my real offer different from the calculator? Actual plans also factor in mortality tables and plan-specific rules set on fixed dates, so treat this as a close estimate, not the exact plan figure.