What This Calculator Estimates
This calculator estimates the future value of an ordinary annuity — a series of equal, regular payments made at the end of each period, growing with compound interest over time. It is useful for planning retirement contributions, savings plans, or any recurring investment.
Formula / Method Used
Future Value = Payment × [((1 + r)^n − 1) / r], where r is the interest rate per period and n is the total number of payment periods. When the rate is zero, the future value is simply the payment multiplied by the number of periods.
Worked Example
Contributing $500 per month at a 6% annual rate for 10 years (120 monthly periods) grows to an estimated future value of roughly $81,940, compared to $60,000 in total contributions — meaning about $21,940 comes from compound growth alone.
How to Interpret the Result
The future value figure shows what your regular payments could grow to under the rate and timeline you entered. The contributions line shows how much of that total came from your own payments versus compound growth, which helps you see how much time and rate are doing the work for you.
Common Mistakes
- Mixing annual and monthly rates without converting them consistently.
- Assuming payments are made at the start of each period (this is an ordinary annuity, paid at period end).
- Ignoring that taxes, fees, and account rules can reduce the real-world growth rate.
- Treating the estimate as guaranteed rather than a planning projection.
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Frequently Asked Questions
What does this annuity calculator estimate?
It estimates the future value of a series of equal, regular payments made into an annuity, based on the payment amount, interest rate, and number of periods.
Does it include taxes or fees automatically?
No. Include any taxes, fees, or special assumptions separately if they matter to your estimate.
Can I use it for retirement planning?
It can support rough planning, but detailed retirement decisions usually need more assumptions and review.
Why should I test different scenarios?
Small changes in rate, timing, or payment amount can affect long-term estimates meaningfully.
When should I update the estimate?
Update it when rate, term, or payment assumptions change.
Last updated: July 2026