THE NUMORIX GUIDE
How to use the Compound Growth Calculator
Last reviewed September 14, 2026
What this calculator does
The engine converts the annual rate to a periodic rate r/compound, compounds the balance for the selected number of periods each year, then adds the Additional dollar amount at the end of each year.
Formula and method
The engine converts the annual rate to a periodic rate r/compound, compounds the balance for the selected number of periods each year, then adds the Additional dollar amount at the end of each year. Effective annual rate is (1 + r/compound)^compound - 1, and total interest is the sum of each periodic interest charge before annual additions.
Variables and inputs
Enter Principal, Annual Rate, Years, Compound frequency of annually, quarterly, monthly, or daily, and Additional dollars per year. The UI treats the additional amount as one end-of-year addition, not as a monthly contribution, and requires a positive term and nonnegative principal and rate.
Worked example
For $10,000 at 7% for one year, compounded monthly, with $200 additional at year end, monthly rate is 0.07/12. The engine compounds the principal to 10,722.90, records about $722.90 interest, then adds $200 for a final value of $10,922.90. The effective annual rate is about 7.23%.
How to interpret the result
The final balance combines the original principal, periodic interest, and the annual addition. Because the addition is made after that year's compounding, it does not earn interest during the year in which it is added; this is different from making equal deposits each month.
Common mistakes to avoid
Enter 7 for 7%, not 0.07, and choose the frequency that matches the account. Do not enter a total annual contribution and assume the engine spreads it monthly. Keep the contribution timing in mind when comparing this result with another projection.
Assumptions and limitations
The model holds the rate constant, adds money only at year end, and does not model taxes, fees, withdrawals, inflation, losses, or changing deposits. The engine accepts a numeric compound value from its function even though the UI offers four choices, so nonstandard calls need their own validation.