How to use this compound interest calculator
Use Project one compound-interest scenario when you want to estimate the future value of one set of assumptions. Enter the starting balance, nominal annual interest rate, compounding frequency, recurring contribution, contribution frequency, and time horizon.
Use Compare two rate / compounding scenarios when you want to see how two different nominal rates or compounding frequencies may affect the result while keeping the starting balance, recurring deposits, contribution schedule, and time horizon the same.
Keeping the deposit assumptions consistent makes it easier to focus on the effect of the rate and compounding differences.
Understanding your results
The estimated ending balance is the projected balance at the end of the selected time horizon. It includes your starting balance, recurring contributions, and estimated interest.
Total deposited shows the starting balance plus the contributions added during the selected period.
Modeled interest earned shows how much of the projected ending balance comes from estimated interest rather than deposits.
The calculator also shows an equivalent APY, which expresses the annual effect of the nominal interest rate and selected compounding frequency as an effective annual yield.
In comparison mode, both scenarios use the same deposit assumptions so you can compare their projected ending balances, modeled interest, and equivalent APYs more easily.
What can affect your compound-interest estimate
Starting balance
Your starting balance is the amount available to begin earning interest at the start of the projection.
A larger starting balance can generally produce more interest over the same period when the rate, compounding frequency, contributions, and time horizon remain unchanged.
Nominal annual interest rate
The interest-rate field in this calculator is a nominal annual interest rate. It does not already include the full annual effect of compounding.
A higher nominal rate generally increases the projected growth of the balance, assuming the other inputs remain the same.
Compounding frequency
You can choose daily, monthly, quarterly, or annual compounding.
Compounding frequency describes how often interest is applied under the scenario. With the same nominal annual rate, changing the compounding frequency can change the effective annual return and the projected ending balance.
More frequent compounding does not automatically make one real-world account better than another. The stated rate, APY, fees, account requirements, and other terms can also matter.
Recurring contributions
Regular contributions can have a significant effect on the amount accumulated over time.
You can model monthly, quarterly, or annual contributions depending on the saving or investing pattern you want to explore.
Increasing the contribution amount or contributing more frequently can increase the total amount deposited and may also increase the amount of money that has an opportunity to earn interest.
Time horizon
The time horizon determines how long the balance and recurring contributions remain in the projection.
A longer period gives compound growth more time to affect the estimate, while a shorter period generally places more of the final balance's weight on the money you directly deposited.
Nominal interest rate vs. APY
A nominal annual interest rate and APY describe interest in different ways.
The nominal rate is the stated annual rate before accounting for the full annual effect of the selected compounding frequency.
APY, or annual percentage yield, reflects the effective annual return after compounding is taken into account.
That is why two scenarios using the same nominal rate can show different equivalent APYs when their compounding frequencies differ.
When to use the Savings APY Calculator instead
Use this Compound Interest Calculator when you have, or want to test, a nominal annual interest rate together with a compounding frequency.
If a savings account is quoted directly with an APY, use the MarketReview Savings APY Calculator instead. APY already reflects the annual effect of compounding, so there is no need to add a separate compounding-frequency assumption.
The two calculators therefore address related but different types of rate information.
Comparing rate and compounding scenarios
Comparison mode can help you see how different nominal interest rates or compounding frequencies affect projected growth while keeping the starting balance and contribution assumptions consistent.
Look at the estimated ending balance and modeled interest together with the equivalent APY rather than focusing only on the stated nominal rate.
For real deposit products, also consider factors that are outside the calculator, including fees, minimum-balance requirements, rate tiers, promotional conditions, and whether the advertised rate can change.
Important assumptions and limitations
This calculator is a planning illustration, not a bank quote or a guarantee of future interest or account value.
The estimate assumes that the nominal annual interest rate you enter remains unchanged throughout the selected time horizon. Actual account rates may rise or fall.
The calculator also assumes that the entered recurring contribution pattern continues throughout the projection.
Actual financial institutions may use different balance methods, interest-crediting practices, transaction timing, rate tiers, fees, minimum-balance requirements, and other account terms.
For these reasons, the balance of an actual deposit account may differ from the estimate shown here.
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