Annuity Calculator
Calculate the future value of a regular savings annuity, including how much you contributed and how much interest you earned.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
An annuity is a series of equal deposits made at regular intervals. This calculator grows each deposit at the stated rate until the end of the term and reports the final balance.
Worked example
calculated with the default values below
Deposit per period 500 $ · Annual interest rate 7 % · Number of years 20 years Future value 260,463.33 $ · Total contributions 120,000.00 $ · Interest earned 140,463.33 $
Method and assumptions
Formula basis and scope
End-of-month deposits use FV = D × ((1 + i)^n - 1) / i, with i = annual percent / 1200 and n = 12 × years; zero rate uses D × n.
Constant nominal rate and equal monthly deposits; excludes taxes, fees and inflation. It is a projection, not a guaranteed return. Fractional month counts are mathematical projections, not an actual payment schedule.
Data sources
Disclaimer
These calculators give estimates for general information only. They are not financial, tax or investment advice and do not take your personal circumstances into account. Before borrowing, investing or filing, confirm the numbers with a qualified adviser in your jurisdiction.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
FV = PMT × ((1 + r)^n − 1) ÷ r
- FV
- future value
- PMT
- regular monthly deposit
- r
- monthly interest rate
- n
- number of deposits
r = annual % ÷ 100 ÷ 12; n = years × 12; ordinary annuity, deposits at period end.
Frequently asked questions
Why does interest earned grow faster than contributions over time?
The model compounds monthly, so earlier deposits earn interest for more months. At $500 deposited each month for 20 years, contributions total $120,000. At a 7% annual rate divided into monthly periods, the calculated future value is about $260,463, including about $140,463 of interest. The result assumes a constant rate and end-of-month deposits.