Annuity CalculatorFree online financial calculator — instant results, no sign-up
Accumulated value of an annuity with additions.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
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About the Annuity Calculator
This calculator estimates the future accumulated value of an ordinary annuity starting with an initial balance and regular annual contributions. It helps individuals and retirement planners project how investments grow through combined compound interest and steady annual deposits.
- Starting principal
- The initial lump sum deposited at year zero, in dollars (typically $0 or greater).
- Annual addition
- The regular fixed contribution added at the end of each year, in dollars (typically $0 or greater).
- Rate
- The annual compounding interest or investment return rate, expressed as a percentage (sensibly 0% to 15%).
- Years
- The total duration of the accumulation period in whole or fractional years (typically 1 to 50).
Formula and method
FV = P × (1 + r)^t + C × (((1 + r)^t - 1) / r)
- FVEnding balance (future value of the annuity)
- PStarting principal balance
- rAnnual interest rate as a decimal (Rate / 100)
- tInvestment timeframe in years
- CAnnual addition amount
The tool converts the percentage rate to a decimal and compounds the starting principal over the full number of years. It then computes the future value of the recurring end-of-year additions (ordinary annuity) using the geometric series formula and sums both components to produce the formatted currency balance.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Starting principal20000 $
- Annual addition5000 $
- Rate5 %
- Years15
Results
- Ending balance$149,471.38
How to use the Annuity Calculator
- 1Divide the annual rate percentage by 100 to determine the decimal interest rate r.
- 2Calculate the growth of the initial principal using P × (1 + r)^t.
- 3Calculate the accumulated value of the annual contributions using C × [((1 + r)^t - 1) / r].
- 4Add both amounts together and round to two decimal places for the total ending balance.
Reading your result
The ending balance represents the total projected wealth at the end of the specified term, combining your contributions and compounding growth. Comparing this figure to your cumulative deposits (P + C × t) shows how much of the ending total comes strictly from investment returns.
Limitations
The calculation assumes additions are made once per year at the end of each period (ordinary annuity) rather than monthly or at the beginning of the year. It also models a constant, uninterrupted rate of return, ignoring market volatility, inflation, account maintenance fees, and taxes.
Common questions
Does this calculate an annuity due or an ordinary annuity?+
It calculates an ordinary annuity, meaning each annual addition is deposited at the end of the compounding year rather than the beginning.
What happens if the annual rate is 0%?+
When the rate is 0%, no compounding occurs, and the future value is simply the starting principal plus the total annual additions (P + C × t).
Can I use this for monthly savings contributions?+
The formula assumes annual compounding with annual additions. To approximate monthly savings, multiply monthly deposits by 12, though compounding monthly would yield a slightly higher actual ending balance.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.