Lump Sum vs Annuity Calculator

Lump Sum vs Annuity Calculator — guide & how to use

What it does

When you win the lottery or are offered a pension/annuity buyout, you face a high-stakes, usually irreversible choice: a one-time lump sum of cash today, or a stream of payments over many years. The offering party tends to highlight whichever number looks bigger. This calculator strips out the framing and compares the two on the only basis that's apples-to-apples — the after-tax present value of each. It shows the after-tax lump sum you'd actually pocket, the present value of the payment stream (pre-tax and after-tax) at the return you expect to earn, the break-even rate of return that makes the two equal, and a sensitivity table so you can see how fragile the verdict is to your assumptions. Everything runs privately in your browser, free.

The single biggest mistake — comparing gross totals

"The payments add up to $900,000 but they only offered me $500,000!" is the error that traps the most people. A dollar received in 20 years is not worth a dollar today — you could have invested today's dollar in the meantime. Present value discounts each future payment back to today's dollars so the comparison is fair. The tool also shows the undiscounted total of all payments, but labels it clearly as ignoring time value — it's there only to counter the "but they add up to more!" intuition, not as a value metric.

Worked example (pension buyout)

Age 62, longevity to 90 (a 28-year horizon), offered a $500,000 lump sum or $2,500/month for life with no COLA. Expected return 5%, lump-sum tax 32%, payment tax 24%, no state tax, ordinary timing:

1. After-tax lump sum: $500,000 × (1 − 0.32) = $340,000.
2. Periodic discount rate (monthly, geometric): (1.05)^1/12 − 1 ≈ 0.4074% per month, over n = 28 × 12 = 336 payments.
3. Pre-tax present value of payments: $2,500 × (1 − (1+i)⁻³³⁶) / i ≈ $457,100.
4. After-tax present value (payments taxed at 24%): ≈ $347,400.
5. Verdict at 5%: the after-tax stream (~$347,400) is worth slightly more than the after-tax lump sum (~$340,000) — the payments edge it out on the numbers at this return and this longevity, but it's close enough that the decision really turns on longevity and risk.
6. Break-even return: the pre-tax break-even here is about 4.2% — the discount rate that makes the stream equal the lump sum. Below it, keep the payments; above it, take the cash and invest. Live to 95 instead of 90 and the stream's value jumps — which is exactly why the sensitivity table matters.

(Displayed dollars are rounded for readability; the tool keeps full precision internally, so hand-rounded steps can differ slightly.)

How to use it

1. Pick Pension/annuity buyout or Lottery winnings. Lottery locks the 30-payment, +5%/yr, 29-year structure automatically.
2. Enter the lump sum cash value (for lottery, the cash value — not the advertised jackpot) and the payment amount (for lottery, the first/smallest of the 30 payments).
3. Set the frequency, any COLA, and the horizon — for a pension, your current age and the age you expect payments to end.
4. Enter your realistic expected return and the two tax rates (a large lump sum is often taxed higher than spread-out payments).
5. Read the verdict, the break-even return, and the sensitivity table across returns and longevity ages before drawing a conclusion.

Accuracy notes & common mistakes

• Educational estimate only — not financial, tax, or legal advice. This choice is high-stakes and usually irreversible; consult a fee-only fiduciary advisor and a CPA before deciding.
• Taxes are modeled as simple flat rates. Real taxation is bracketed and progressive: a large lump sum can push you into the 37% top federal bracket (2026: over $640,600 single / $768,700 MFJ), while spread payments often land lower — that asymmetry is exactly why the two rates are modeled separately. Actual liability depends on your full return, deductions, and state law.
• Lottery lump-sum withholding is ~24% federal at payout, but your final tax is usually higher (up to 37%) — set the lump-sum tax rate to your expected true marginal rate, not 24%.
• Powerball / Mega Millions annuities are 30 graduated payments over 29 years, +5%/yr, backed by U.S. Treasury bonds — effectively default-risk-free. Private pension annuities carry the plan's/insurer's credit risk (PBGC insures private pensions only up to federal limits).
• The present-value result is only as good as the discount rate you pick. There's no single "correct" rate — using your realistic, risk-adjusted expected return matters more than any other input. Don't use a 10–12% stock-market rate to justify the lump sum and then park the money in cash.
• The break-even rate is the annuity's implied guaranteed return. It's a hurdle, not a prediction — comparing it to a safe alternative (Treasuries/CDs) is fairer than comparing to optimistic stock returns, because the payments are contractually fixed.
• Longevity is the dominant unknown for a lifetime pension — a pension is longevity insurance you can't outlive. We use a single assumed end-age, not a mortality-weighted value; run the sensitivity table before trusting any verdict.
• Pension lump-sum offers are themselves computed by the plan using IRS minimum-present-value segment rates; this tool evaluates the offer you were given, it doesn't replicate the plan's segment-rate math.
• This uses geometric rate conversion i = (1+r)^1/m − 1 for non-annual frequencies (not r/m). It does not model: survivor/joint-and-survivor benefits, early-withdrawal penalties, RMDs, IRA-rollover deferral, Medicare IRMAA surcharges, or estate considerations — any of which can flip the decision.
• Behavioral risk: large lump sums are frequently mismanaged or spent down. The "mathematically better" lump sum only wins if you actually invest it at the assumed rate.

Frequently asked questions

Educational estimate only — not financial, tax, or legal advice. A lump-sum-vs-annuity decision is high-stakes and usually irreversible; confirm with a fee-only fiduciary advisor and a CPA before acting. Taxes here are simple flat rates; real liability is bracketed and progressive and varies by state and year. Sources: Schwab "investing a lump sum vs annuity" break-even examples, Ameriprise pension-vs-lump-sum methodology, IRS minimum-present-value segment rates & 2026 inflation adjustments, Tax Foundation 2026 brackets, Annuity.org & USA Mega on Powerball's 30-payment +5%/yr Treasury-backed structure.

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