The formula
How it works
An annuity is a series of equal payments made at regular intervals. This calculator finds the future value of that stream — what all the payments plus their interest will add up to by the end.
FAQ
What’s the difference between ordinary and annuity-due?
An ordinary annuity pays at the end of each period; an annuity-due pays at the start. Because the “due” payments have an extra period to earn interest, an annuity-due always ends up slightly larger.
Is this the same as an insurance annuity?
The maths of accumulating regular payments is the same, but an insurance annuity is a specific product that later pays an income. This calculator handles the savings (accumulation) side — how the payments build up.
How much difference does the payment timing actually make?
Switching from end-of-period to start-of-period payments multiplies the future value by (1 + rate per period), so at low rates the gap is small, but over many years at a higher rate it can add up to a meaningful sum.
What happens if the interest rate is zero?
With a 0% rate the future value is simply the payment multiplied by the number of periods — there’s no growth, only the sum of what you put in, since there’s nothing to compound.
How does inflation affect the future value shown here?
The result is a nominal figure — it doesn’t subtract inflation. To see purchasing power in today’s terms, use an inflation-adjusted (real) rate instead of the nominal rate when comparing to current prices.
What if my payment amount grows over time instead of staying fixed?
This calculator assumes a level, unchanging payment each period. A growing annuity, where payments increase by a fixed percentage each period, needs a different formula and will produce a larger future value than a level annuity of the same starting payment.
Are annuity earnings taxed as they grow?
It depends on the account: earnings inside a tax-advantaged retirement account are typically not taxed until withdrawal, while a taxable account may owe tax on interest each year. This calculator shows the pre-tax growth of the payment stream.
About the annuity calculator
This calculator finds the future value of an annuity — a stream of equal payments made at regular intervals, each earning interest until the end. Annuities are the backbone of retirement saving, pensions and structured payment plans, because they turn a manageable regular amount into a large sum over time. Seeing the final value next to the total paid in shows exactly how much the compounding interest contributes.
How to use it
Enter the payment made each period, the interest rate per period, the number of periods, and whether payments come at the end or start of each period. The calculator returns the future value, along with the total you paid in and the interest earned. For example, $5,000 a year at 5% for 20 years grows to about $165,000, of which around $65,000 is interest on top of your $100,000 of payments.
The formula
The future value of an ordinary annuity is , where is each payment, is the rate per period and is the number of payments. For an annuity-due, where payments are made at the start of each period, the result is multiplied by an extra because every payment earns one more period of interest.
Where it is used
Annuities are central to retirement planning, where regular contributions build a pension pot, and to structured settlements and lottery payouts. Insurers use annuity maths to price products, and savers use it to see how consistent contributions grow. The same formula underlies loan payments, lease schedules and any arrangement built on equal, regular cash flows.