Monthly Annuity Payment Calculator

Calculate Fixed Monthly Payments for Annuities

Annuity Monthly Payment Formula

Formula

\[ PMT = P \times \frac{r(1 + r)^n}{(1 + r)^n - 1} \]

Where:

$PMT$ — monthly annuity payment
$P$ — principal, or present value of the investment
$r$ — monthly interest rate (annual rate divided by 12)
$n$ — total number of monthly payments

This formula gives the fixed payment that fully exhausts the principal over the term, with each payment covering the interest accrued that month plus a portion of the principal. If the interest rate is zero, the formula simplifies to $PMT = P / n$.

Annuity Monthly Payment – Calculation Example

Example: you invest $10,000 in an annuity that pays a 6% annual rate, compounded monthly, over 60 months (5 years).

\[ r = \frac{6\%}{12} = 0.005 \]

\[ PMT = 10{,}000 \times \frac{0.005 \times (1.005)^{60}}{(1.005)^{60} - 1} = 10{,}000 \times \frac{0.005 \times 1.34885}{0.34885} \approx 193.33 \]

Result: the monthly payment is about $\$193.33$. Over 60 months you receive $60 \times 193.33 \approx \$11{,}999.80$ in total — wait, more precisely $\$11{,}599.80$, of which roughly $\$1{,}599.80$ is interest earned on the remaining balance.

How to Use the Calculator

Enter the Investment Amount — the present value you are converting into payments (e.g. $10,000).
Enter the Annual Interest Rate as a percentage, not a decimal (e.g. 6 for 6%, or 5.25 for 5.25%).
Enter the Number of Months — the total count of monthly payments over the full term.
Read the Monthly Payment result, which shows the fixed amount you would pay or receive each month.

The calculator converts the annual rate to a monthly rate automatically (annual rate ÷ 12), so you never need to convert it yourself.

What Is a Monthly Annuity Payment?

An annuity is a series of equal payments made at regular intervals. When the payments are monthly and the term and rate are fixed, each payment is identical, and the formula above tells you exactly how large it must be. The same math governs two mirror-image situations: receiving fixed payouts from an investment (an annuity in the strict sense, common in retirement planning and structured settlements) and paying off a loan in equal installments (a standard amortized mortgage, car loan, or personal loan).

The key idea behind the formula is the time value of money. A dollar received next month is worth slightly less than a dollar today, because today's dollar could earn interest in the meantime. The term $(1 + r)^n$ compounds the monthly rate over the whole term, and the payment is set so that the present value of all future payments, discounted at rate $r$, equals the principal $P$. In other words, the lender or annuity provider neither gains nor loses on the deal relative to the stated rate.

Interpreting the result is straightforward: the monthly payment is the fully amortizing amount. If you are the investor, it is the check you can expect each month until the balance reaches zero. If you are the borrower, it is the installment that pays off both interest and principal by the end of the term. Multiplying $PMT \times n$ gives total cash flow, and the excess over $P$ is the total interest earned (or paid) over the life of the annuity.

This calculator is useful for comparing scenarios quickly — a longer term lowers the payment but increases total interest, while a higher rate raises the payment for the same principal. For related figures, see the Immediate (Ordinary) Annuity and Deferred Annuity Payment calculators, and the Debt Consolidation Payment calculator for the borrower's side.

Assumptions and Limitations

Fixed rate and fixed payments. The formula assumes the interest rate never changes and every payment is the same. Variable-rate annuities, adjustable-rate mortgages, and step-up payment schedules are not covered.
Monthly compounding. The annual rate is divided by 12 with no adjustment for intra-month compounding effects. Products quoted with an effective annual yield (APY) will differ slightly; the Annual Percentage Yield calculator can help you convert.
Ordinary annuity timing. Payments are assumed to occur at the end of each month (an ordinary annuity). An annuity due, with payments at the start of each month, would produce a slightly different amount.
No fees, taxes, or inflation. Insurance fees, surrender charges, income tax on payouts, and the declining purchasing power of money are all ignored. A payment of $193.33 will buy less in year 5 than it does today.
Full amortization. The principal is fully drawn down to zero by the final payment. Products with a residual value, balloon payment, or lifetime guarantee (such as a life annuity with no fixed term) need a different calculation.

For long-term planning, also remember that a fixed monthly payout over 20–30 years carries significant inflation risk; pairing this estimate with a growth assumption from the Compound Annual Growth Rate calculator gives a more realistic picture.

Frequently Asked Questions

What is a common mistake when calculating annuity payments by hand?

The most frequent error is using the annual interest rate instead of the monthly rate. Always divide the annual rate by 12 first: 6% per year becomes $r = 0.06/12 = 0.005$. Another common slip is entering the rate as a decimal when the tool expects a percentage (type 6, not 0.06), or mixing years and months — $n$ must be the total number of monthly payments, so a 5-year term means $n = 60$.

How do I convert years to months for the number of payments?

Multiply the number of years by 12. For example, 10 years equals $10 \times 12 = 120$ monthly payments, and 30 years equals 360. If your term is mixed, like 2 years and 6 months, convert both parts to months: $24 + 6 = 30$. Any fractional months (say 30.5) are mathematically allowed, but real annuity and loan terms almost always use whole months.

Why does my lender's or insurer's quote differ slightly from this calculator?

Several factors cause small differences. Quotes based on an effective annual yield (APY) rather than a nominal rate produce slightly different payments because monthly compounding is already built into APY. Fees, insurance charges, and rounding conventions (some lenders round payments up to the cent or dollar) also shift the result. Payments made at the beginning of each month (an annuity due) are lower than the end-of-month payments calculated here — roughly by a factor of $1/(1 + r)$.

What is a normal monthly payment for a $100,000 annuity?

At 5% annual interest over 20 years (240 months), $100,000 pays about $660 per month. Over 10 years the same amount pays roughly $1,061, and over 30 years about $537. These figures exclude fees, taxes, and inflation. If you are shopping for a real annuity, compare quotes from multiple insurers, because payout rates and fee structures vary, and payouts from lifetime annuities depend on your age and life expectancy.

How much of each payment is interest versus principal?

The split changes every month. The interest portion of any payment is the monthly rate times the remaining balance: $r \times \text{balance}$. The rest reduces principal. Early payments are mostly interest because the balance is large; by the final payments almost everything goes to principal. Total interest over the whole term is simply $PMT \times n - P$. If you need a full month-by-month breakdown, use an amortization schedule rather than this single-payment estimate.

Can this formula be used for mortgages and car loans?

Yes — it is the standard amortization formula. Any loan with a fixed rate, equal monthly payments, and full repayment over a set term uses exactly the same math, whether it is called an annuity payout or a mortgage installment. The key requirements are that the rate is fixed, payments are equal, and the balance reaches zero at the end. Balloon loans, adjustable-rate mortgages, and leases with a residual value need a modified calculation.

What happens if the interest rate is zero?

When the rate is zero, the payment is simply the principal divided by the number of months: $PMT = P/n$. No interest accrues, so over the term you receive (or repay) exactly the original amount in equal parts. The calculator handles this case automatically; you can enter 0 for the rate without causing a division error, which the raw formula would produce if applied carelessly.

Monthly Annuity Payment Estimator