Calculator
Compound Interest Calculator
Project how a starting balance may grow over time when interest or returns compound, and test how rate, time, and compounding frequency change the ending estimate.
Result
Ending balance
$20,096.61
Interest earned
$10,096.61
How to use this calculator
What this calculator does
Project how a starting balance may grow over time when interest or returns compound, and test how rate, time, and compounding frequency change the ending estimate.
How to use it
Enter the starting amount, assumed annual return, time period, and compounding frequency. Review the ending balance as a scenario estimate, then test conservative and optimistic return assumptions.
What the result means
Use the result as a planning estimate. Compare it against your budget, then account for fees, taxes, timing, and lender or account rules before making a decision.
Browse more finance calculators for related estimates and comparisons.
Results are estimates for planning and education. They do not include every fee, tax, lender rule, market outcome, inflation factor, or personal financial circumstance.
Scenario guidance
When to use this
Use this when you want to model how a savings or investment balance could change over time under a specific return and compounding assumption.
Example scenario
A saver comparing long-term goals can run the same starting balance at 4%, 6%, and 8% to understand how sensitive the projection is to the return assumption.
Inputs that usually matter most
- Starting amount, because it is the base that compounds over time.
- Annual return, which is an assumption rather than a guaranteed outcome.
- Time and compounding frequency, since more periods give interest more chances to compound.
Common mistake to avoid
Do not use one return assumption as a forecast. A small change in the assumed rate can make the final balance look much better or worse than a real outcome.
How to interpret the result
Use the result to compare scenarios and understand the effect of time. The ending balance is most useful when viewed alongside lower-rate and shorter-time alternatives.
Results are estimates based on the formula shown. Actual savings or investment outcomes can change with market returns, account rates, fees, inflation, taxes, contribution timing, and withdrawal behavior.
Formula
A is ending balance, P is principal, r is the assumed annual rate, n is compounding periods per year, and t is years. The projection assumes the same rate and compounding schedule for the full period.
Example growth
$10,000 at 7% compounded monthly for 10 years grows to about $20,097 before taxes and fees. Using the same starting amount for 20 years instead would produce a much larger estimate because time gives compounding more room to work.
Frequently Asked Questions
Is this a guaranteed return?
No. It is a math projection based on the rate you enter, not a promise of market performance, savings yield, or future purchasing power.
Can the annual return be negative?
Yes. A negative rate can model losses or declining balances.
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