Annuity Payout: How Much Monthly Income Will Your Lump Sum Generate?

An annuity converts a lump sum into a guaranteed income stream. The question everyone asks is simple: how much will I get each month? The answer depends on three numbers — your lump sum, the guaranteed interest rate, and how many years you want payments. Here is the math and the decision framework.

The payout formula

Annuity payouts use the standard time-value-of-money formula. The insurance company takes your lump sum, earns interest on it, and pays you back in equal monthly installments over the agreed period. Each payment contains two parts: interest earned and return of principal. Early payments are mostly interest. Later payments shift toward principal.

The formula: PMT = PV × r / (1 − (1 + r)−n), where PV is your lump sum, r is the monthly interest rate, and n is the total number of payments. A $500,000 lump sum at 5% for 20 years produces roughly $3,300/month.

What actually determines your payout

1. The interest rate

This is the rate the insurance company guarantees. It is not the same as market rates — insurers add their own margin. A 1% increase in the guaranteed rate increases monthly payouts by roughly 5–8%, depending on the term. Rates vary by insurer, so shop around. Get quotes from at least three companies before committing.

2. The payout period

Longer periods mean lower monthly payments but more total income. A $500,000 annuity at 5% pays about $3,300/month over 20 years but only $2,650/month over 30 years. The total payout over 30 years ($954,000) is higher than over 20 years ($792,000), but you receive less each month.

3. When payments start

An immediate annuity starts paying within a month of your lump sum deposit. A deferred annuity delays payments for years, letting the lump sum grow tax-deferred. Deferred annuities produce higher monthly payouts because the lump sum compounds before payments begin. A $500,000 deferred annuity waiting 10 years at 5% grows to $814,000 — then pays $5,300/month for 20 years.

Annuity vs the 4% rule: the honest comparison

The 4% rule says you can withdraw 4% of your portfolio annually, adjusted for inflation, and have a high probability of not running out over 30 years. On $500,000, that is $20,000/year or $1,667/month. An annuity at 5% for 20 years pays $3,300/month — nearly double.

But the comparison is misleading. The 4% rule preserves your principal (in most scenarios) and adjusts for inflation. The annuity does neither — it exhausts your lump sum over the payout period and the payments are fixed. In year 15, your $3,300/month buys significantly less due to inflation.

The right answer depends on what you need:

• Annuity wins if you need guaranteed income, have no investment discipline, or are worried about outliving your money.
• 4% rule wins if you can handle market volatility, want inflation protection, and prefer to preserve principal for heirs.
• Hybrid approach — use an annuity to cover essential expenses (housing, food, insurance) and invest the rest using the 4% rule.

COLA adjustments: are they worth it?

Some annuities offer a Cost of Living Adjustment — your payments increase by a fixed percentage (usually 2–3%) each year. This protects against inflation but reduces your starting payment by 15–25%. A $500,000 annuity with 2% COLA starts at about $2,500/month instead of $3,300.

The math: over 20 years, the COLA version produces higher total payouts if inflation averages above 2%. Below that, the fixed version wins. Since inflation has averaged 3% historically, COLA is usually worth it — but only if you can afford the lower starting payment.

What to watch out for

• Surrender charges: most annuities lock your money for 5–10 years. Early withdrawal penalties can be 7–10% of the balance.
• High fees: variable annuities charge 2–3% annually in fees. Fixed annuities are simpler and cheaper.
• Tax treatment: annuity income is taxed as ordinary income, not capital gains. In a taxable account, this is worse than the preferential rates on investment gains.
• Inflation risk: fixed annuity payments lose purchasing power every year. A $3,300/month payment in year 15 buys what $2,200 buys today at 3% inflation.